IS-IS
Configuring IS-IS
Intermediate-system-to-intermediate-system (IS-IS) is a link-state interior gateway protocol (IGP) which uses the Shortest Path First (SPF) algorithm to determine routes. Routing decisions are made using the link-state information. IS-IS evaluates topology changes and, if necessary, performs SPF recalculations.
Entities within IS-IS include networks, intermediate systems, and end systems. In IS-IS, a network is an autonomous system (AS), or routing domain, with end systems and intermediate systems. A router is an intermediate system. End systems are network devices which send and receive protocol data units (PDUs), the OSI term for packets. Intermediate systems send, receive, and forward PDUs.
End system and intermediate system protocols allow routers and nodes to identify each other. IS-IS sends out link-state updates periodically throughout the network, so each router can maintain current network topology information.
IS-IS supports large ASs by using a two-level hierarchy. A large AS can be administratively divided into smaller, more manageable areas. A system logically belongs to one area. Level 1 routing is performed within an area. Level 2 routing is performed between areas. The routers can be configured as level 1, level 2, or both level 1/2.
IS-IS routing domain displays an example of an IS-IS routing domain.
Routing
OSI IS-IS routing uses two-level hierarchical routing. A routing domain can be partitioned into areas. Level 1 routers know the topology in their area, including all routers and end systems in their area but do not know the identity of routers or destinations outside of their area. Level 1 routers forward traffic with destinations outside of their area to a level 2 router in their area.
Level 2 routers know the level 2 topology, and know which addresses are reachable by each level 2 router. Level 2 routers do not need to know the topology within any level 1 area, except to the extent that a level 2 router can also be a level 1 router within a single area. By default, only level 2 routers can exchange PDUs or routing information directly with external routers located outside the routing domain.
The two types of routers in IS-IS are described below.
Level 1 intermediate systems
Routing is performed based on the area ID portion of the ISO address called the Network Entity Title (NET). Level 1 systems route within an area. They recognize, based on the destination address, whether the destination is within the area. If so, they route toward the destination. If not, they route to the nearest level 2 router.
Level 2 intermediate systems
Routing is performed based on the area address. They route toward other areas, regardless of other area’s internal structure. A level 2 intermediate system can also be configured as a level 1 intermediate system in the same area.
The level 1 router’s area address portion is manually configured (see ISO network addressing). A level 1 router does not become a neighbor with a node that does not have a common area address. However, if a level 1 router has area addresses A, B, and C, and a neighbor has area addresses B and D, then the level 1 router accepts the other node as a neighbor, as address B is common to both routers. Level 2 adjacencies are formed with other level 2 nodes whose area addresses do not overlap. If the area addresses do not overlap, the link is considered by both routers to be level 2 only and only level 2 LSPDUs flow on the link.
Within an area, level 1 routers exchange LSPs which identify the IP addresses reachable by each router. Specifically, zero or more IP address, subnet mask, and metric combinations can be included in each LSP. Each level 1 router is manually configured with the IP address, subnet mask, and metric combinations, which are reachable on each interface. A level 1 router routes as follows:
if a specified destination address matches an IP address, subnet mask, or metric reachable within the area; the PDU is routed via level 1 routing
if a specified destination address does not match any IP address, subnet mask, or metric combinations listed as reachable within the area; the PDU is routed toward the nearest level 2 router
Level 2 routers include in their LSPs, a complete list of IP address, subnet mask, and metrics specifying all the IP addresses which reachable in their area. This information can be obtained from a combination of the level 1 LSPs (by level 1 routers in the same area). Level 2 routers can also report external reachability information, corresponding to addresses reachable by routers in other routing domains or autonomous systems.
IS-IS frequently used terms
Area
An area is a routing sub-domain which maintains detailed routing information about its own internal composition, and also maintains routing information which allows it to reach other routing sub-domains. Areas correspond to the level 1 sub-domain.
End system
End systems send NPDUs to other systems and receive NPDUs from other systems, but do not relay NPDUs. This International Standard does not specify any additional end system functions beyond those supplied by ISO 8473 and ISO 9542.
Neighbor
A neighbor is an adjacent system reachable by traversing a single sub-network by a PDU.
Adjacency
An adjacency is a portion of the local routing information which pertains to the reachability of a single neighboring end or intermediate system over a single circuit. Adjacencies are used as input to the decision process to form paths through the routing domain. A separate adjacency is created for each neighbor on a circuit and for each level of routing (level 1 and level 2) on a broadcast circuit.
Circuit
The subset of the local routing information base pertinent to a single local Subnetwork Point of Attachments (SNPAs).
Link
The communication path between two neighbors. A link is up when communication is possible between the two SNPAs.
Designated IS
The intermediate system on a LAN which is designated to perform additional duties. In particular, the designated IS generates link-state PDUs on behalf of the LAN, treating the LAN as a pseudonode.
Pseudonode
Where a broadcast sub-network has n connected intermediate systems, the broadcast sub-network itself is considered to be a pseudonode. The pseudonode has links to each of the n intermediate systems and each of the ISs has a single link to the pseudonode (instead of n-1 links to each of the other intermediate systems). Link-state PDUs are generated on behalf of the pseudonode by the designated IS.
Broadcast sub-network
A multi-access subnetwork that supports the capability of addressing a group of attached systems with a single PDU.
General topology sub-network
A topology that is modeled as a set of point-to-point links, each of which connects two systems. There are several generic types of general topology subnetworks, multipoint links, permanent point-to-point links, dynamic and static point-to-point links.
Routing sub-domain
A routing sub-domain consists of a set of intermediate systems and end systems located within the same routing domain.
Level 2 sub-domain
Level 2 sub-domain is the set of all level 2 intermediate systems in a routing domain.
ISO network addressing
IS-IS uses ISO network addresses. Each address identifies a point of connection to the network, such as a router interface, and is called a Network Service Access Point (NSAP).
An end system can have multiple NSAP addresses, in which case the addresses differ only by the last byte (called the n selector). Each NSAP represents a service that is available at that node. In addition to having multiple services, a single node can belong to multiple areas.
Each network entity has a special network address called a Network Entity Title (NET). Structurally, a NET is identical to an NSAP address but has an n-selector of 00. Most end systems have one NET. Intermediate systems can have up to three area IDs (area addresses).
NSAP addresses are divided into three parts. Only the area ID portion is configurable.
Area ID
A variable length field between 1 and 13 bytes long. This includes the Authority and Format Identifier (AFI) as the most significant byte and the area ID.
System ID
A six-byte system identification. This value is not configurable. The system ID is derived from the system or router ID.
Selector ID
A one-byte selector identification that must contain zeros when configuring a NET. This value is not configurable. The selector ID is always 00.
Of the total 20 bytes comprising the NET, only the first 13 bytes, the area ID portion, can be manually configured. As few as one byte can be entered or, at most, 13 bytes. If less than 13 bytes are entered, the rest is padded with zeros.
Routers with common area addresses form level 1 adjacencies. Routers with no common NET addresses form level 2 adjacencies, if they are capable (Using area addresses to form adjacencies).
IS-IS PDU configuration
The following PDUs are used by IS-IS to exchange protocol information:
IS-IS hello PDU
Routers with IS-IS enabled send hello PDUs to IS-IS-enabled interfaces to discover neighbors and establish adjacencies.
Link-state PDUs
Contain information about the state of adjacencies to neighboring IS-IS systems. LSPs are flooded periodically throughout an area.
Complete sequence number PDUs
In order for all routers to maintain the same information, CSNPs inform other routers that some LSPs can be outdated or missing from their database. CSNPs contain a complete list of all LSPs in the current IS-IS database.
Partial sequence number PDUs (PSNPs)
PSNPs are used to request missing LSPs and acknowledge that an LSP was received.
IS-IS operations
-
Hello PDUs are sent to the IS-IS-enabled interfaces to discover neighbors and establish adjacencies.
-
IS-IS neighbor relationships are formed if the hello PDUs contain information that meets the criteria for forming an adjacency.
-
The routers can build a link-state PDU based upon their local interfaces that are configured for IS-IS and prefixes learned from other adjacent routers.
-
The routers flood LSPs to the adjacent neighbors except the neighbor from which they received the same LSP. The link-state database is constructed from these LSPs.
-
A Shortest Path Tree (SPT) is calculated by each IS, and from this SPT the routing table is built.
IS-IS route summarization
IS-IS route summarization allows users to create aggregate IPv4 or IPv6 addresses that include multiple groups of IPv4 or IPv6 addresses for a specific IS-IS level. IPv4 and IPv6 routes redistributed from other routing protocols also can be summarized. This is similar to OSPF configuration using the area-range command. IS-IS IPv4 and IPv6 route summarization helps to reduce the size of the LSDB and the IPv4 or IPv6 routing table, and reduces the chance of route flapping.
IS-IS route summarization supports:
level 1, level 1-2, and level 2
route summarization for the IPv4 or IPv6 routes redistributed from other protocols
the smallest metric used to advertise summary addresses of all the more specific IPv4 or IPv6 routes
IS-IS IPv6 route summarization algorithm and SRv6 locator awareness
Partial SPF calculation
IS-IS supports partial SPF calculation, also referred to as partial route calculation. When an event does not change the topology of the network, IS-IS is not perform full SPF but instead performs an IP reach calculation for the impacted routes. Partial SPF is performed at the receipt of IS-IS LSPs with changes to IP reach TLVs and in general, for any IS-IS LSP TLV and sub-TLV change that does not impact the network topology.
IS-IS multi-topology support
Multi-Topology IS-IS (MT-ISIS) support within SR OS allows for the creation of different topologies within IS-IS that contribute routes to specific route tables for IPv4 unicast, IPv6 unicast, IPv4 multicast, and IPv6 multicast. This capability allows for non-congruent topologies between these different routing tables. As a result, networks are able to control which links or nodes are to be used for forwarding different types of traffic.
For example, MT-ISIS could allow all links to carry IPv4 traffic, while only a subset of links can also carry IPv6 traffic.
SR OS supports the following multi-topologies:
IPv4 Unicast – MT-ID 0
IPv6 Unicast – MT-ID 2
IPv4 Multicast – MT-ID 3
IPv6 Multicast – MT-ID 4
Native IPv6 support
IS-IS IPv6 TLVs for IPV6 routing is supported in SR OS. This support is considered native IPv6 routing within IS-IS. However, it has limitations in that IPv4 and IPv6 topologies must be congruent, otherwise traffic may be blackholed. Service providers should ensure that the IPv4 topology and IPv6 topologies are the same if native IPv6 routing is used within IS-IS.
IS-IS administrative tags
IS-IS administrative tags enable a network administrator to configure route tags to tag IS-IS route prefixes. These tags can subsequently be used to control IS-IS route redistribution or route leaking.
IS-IS route tagging can be applied to IP addresses of an interface and to administrative policies with a route map. A network administrator can tag a summary route and then use a route policy to match the tag with one or more attributes for the route.
Using these administrative policies, the operator can control how a router handles route exchanges with its IS-IS neighboring routers. Administrative policies are also used to govern the installation of routes in the routing table.
Route tags allow policies to do the following:
redistribute routes received from other protocols in the routing table to IS-IS
redistribute routes or SRv6 locators between levels in an IS-IS routing hierarchy
summarize routes redistributed into IS-IS or within IS-IS by creating aggregate (summary) addresses
Setting route tags
IS-IS route tags are configurable in the following ways:
for an IS-IS interface
on an IS-IS passive interface
for a route redistributed from another protocol to IS-IS
for a route redistributed from one IS-IS level to another IS-IS level
for an IS-IS default route
for an IS-IS summary address or SRv6 locator
Using route tags
The configured setting of the IS-IS administrative tags on this or on a neighboring IS-IS router only takes effect if policies are configured to instruct how to process the specified tag value.
- MD-CLI
configure policy-options policy-statement entry from configure policy-options policy-statement entry action tag configure policy-options policy-statement default-action tag
- classic CLINote: To configure policy-statements, use the begin command to enter the edit mode and use the commit command to save your changes.
configure router policy-options policy-statement entry from configure router policy-options policy-statement entry action tag configure router policy-options policy-statement default-action tag
Unnumbered interface support
IS-IS supports unnumbered point-to-point interface with both Ethernet and PPP encapsulations.
Unnumbered interfaces borrow the address from other interfaces such as system or loopback interfaces and uses it as the source IP address for packets originated from the interface. This feature supports both dynamic and static ARP for unnumbered interfaces to allow interworking with unnumbered interfaces that may not support dynamic ARP.
An unnumbered interface is an IPv4 capability only used in cases where IPv4 is active (IPv4-only and mixed IPv4/IPv6 environments). When configuring an unnumbered interface, the interface specified for the unnumbered interface (system or other) must have an IPv4 address. Also, the interface type for the unnumbered interface automatically is point-to-point. The unnumbered option can be used in IES and VPRN access interfaces, as well as in a network interface with MPLS support.
Multi-homed prefix LFA extensions in IS-IS
Feature configuration
Use the following command to configure the Multi-Homed Prefix (MHP) LFA feature for IP FRR for IS-IS routes, SR-ISIS tunnel, and SRv6-ISIS tunnel FRR:
- MD-CLI
configure router isis loopfree-alternate multi-homed-prefix preference
- classic
CLI
configure router isis loopfree-alternates multi-homed-prefix preference
When applied to IP prefixes, IP FRR must also be enabled. Use the following command to allow the programming of the backup paths in the FIB:
- MD-CLI
configure routing-options ip-fast-reroute
- classic
CLI
configure router ip-fast-reroute
This feature uses the multihomed prefix model described in RFC 8518 to compute a backup IP next hop via an alternate ABR or ASBR for external prefixes and to an alternate router owner for local anycast prefixes. Without this feature, the backup path is computed to the ASBR, ABR, or router owner, which is the best path for the prefix.
This feature further enhances the multihomed prefix backup path calculation beyond RFC 8518 with the addition of repair tunnels that make use of a PQ node or a P-Q set to reach the alternate exit ABR or ASBR of external prefixes or the alternate owner router of intra-area anycast prefixes.
The base LFA algorithm is applied to all intra-area and external prefixes of IP routes (IP FRR), of SR-ISIS node SID tunnels (SR-ISIS FRR), and to SRv6-ISIS remote locator tunnels (SRv6-ISIS FRR), as usual. Then the MHP LFA is applied to improve the protection coverage for external prefixes and anycast prefixes. For external /32 IPv4 prefixes and /128 IPv6 prefixes and for intra-area /32 IPv4 and /128 IPv6 prefixes with multiple owner routers (anycast prefixes), the base LFA backup path, if found, is preferred over the MHP LFA backup path in the default behavior with the preference command set to a value of none. The user can force the programming of the MHP LFA backup path by setting preference command value to all.
After the IP next-hop based MHP LFA is enabled, the extensions to MHP LFA to compute an SR-TE repair tunnel for an SR-ISIS or SRv6-ISIS tunnel are automatically enabled when the following CLI command is configured to enable Topology-Independent Loop-Free Alternate (TI-LFA) or Remote Loop-Free Alternate (RLFA). The computation reuses the SID list of the primary path or the TI-LFA or RLFA backup path of the alternate ABR, ASBR, or alternate owner router.
- MD-CLI
configure router isis loopfree-alternate remote-lfa configure router isis loopfree-alternate ti-lfa
- classic
CLI
configure router isis loopfree-alternates remote-lfa configure router isis loopfree-alternates ti-lfa
TI-LFA, base LFA, and RLFA (if enabled) are applied to the SR-ISIS node SID tunnels of all intra-area and external /32 IPv4 and /128 IPv6 prefixes as usual, and to all SRv6-ISIS locator tunnels of intra-area and external prefixes of any size.
For node SID SR-ISIS tunnels of external /32 IPv4 and /128 IPv6 prefixes or intra-area /32 IPv4 and /128 IPv6 anycast prefixes, the LFA, TI-LFA, or RLFA backup path is preferred over the MHP LFA backup path in the default behavior with the preference command set to a value of none. The user can force the programming of the MHP LFA backup by setting the preference command value to all. Finally, the same preference rule also applies to SRv6-ISIS remote locator tunnels of external prefixes and intra-area prefixes with multiple router owners.
The MHP LFA backup path protects SR-ISIS tunnels and SRv6-ISIS locator tunnels in both algorithm 0 and flexible-algorithm numbers. Therefore, it also extends the protection to any SR-TE LSP, SR-MPLS policy, or SRv6 policy that uses an SR-ISIS SID or an SRv6-ISIS SID of those same prefixes in its configured or computed SID list.
Feature applicability
The multi-homed-prefix command enables the feature, but its applicability depends on the LFA flavor enabled in the IS-IS instance. The following scenarios are possible:
- Scenario 1
- MD-CLI
The loopfree-alternate and multi-homed-prefix commands are enabled.
- classic CLI
The loopfree-alternates and multi-homed-prefix commands are enabled.
The IP next-hop based MHP LFA feature enhances base LFA only; it applies to IP FRR (when the ip-fast-reroute command is also enabled) and to SR-ISIS tunnels and SRv6-ISIS tunnels.
- MD-CLI
- Scenario 2
- MD-CLI
The loopfree-alternate remote-lfa and loopfree-alternate ti-lfa commands are enabled, or both commands and the multi-homed-prefix command is enabled.
- classic CLI
The loopfree-alternates remote-lfa and loopfree-alternates ti-lfa commands are enabled, or both commands and the multi-homed-prefix command is enabled.
The enabling of RLFA, TI-LFA, or both on top of the MHP LFA automatically enables the SR OS specific enhancements to RFC 8515 that compute a repair tunnel to the alternate exit ABR or ASBR of external prefixes or to the alternate owner router for intra-area anycast prefixes. This enhancement improves coverage because it computes a SR-TE or SRv6 backup repair tunnel to an alternate ASBR. This forces the packet to go to the alternate ASBR because the RFC 8518 MHP LFA may not find a loop-free path to this alternate ASBR.
- MD-CLI
RFC 8518 MHP LFA for IS-IS
The behavior of this feature is the same as in OSPF. See Multi-homed prefix LFA extensions in OSPF.
FIB prioritization
The RIB processing of specific routes can be prioritized through the use of the rib-priority command. This command allows specific routes to be prioritized through the protocol processing so that updates are propagated to the FIB as quickly as possible.
The rib-priority command is configured within the global IS-IS routing context, and the administrator has the option to either specify a prefix list or an IS-IS tag value. If a prefix list is specified, route prefixes matching any of the prefix list criteria is considered high priority. If instead an IS-IS tag value is specified, any IS-IS route with that tag value is considered high priority.
Routes designated as high priority are the first routes processed and passed to the FIB update process so that the forwarding engine can be updated. All known high priority routes should be processed before the IS-IS routing protocol moves on to other standard priority routes. This feature has the most impact when a large number of routes are learned through the IS-IS routing protocols.
IS-IS graceful restart helper
IS-IS supports the graceful restart helper function which provides an IS-IS neighbor a grace period during a control plane restart to minimize service disruption. When the control plane of a GR-capable router fails or restarts, the neighboring routers supporting the graceful restart helper mode (GR helpers) temporarily preserve IS-IS forwarding information. Traffic continues to be forwarded to the restarting router using the last known forwarding tables. If the control plane of the restarting router comes back up within the grace period, the restarting router resumes normal IS-IS operation. If the grace period expires, then the restarting router is presumed inactive and the IS-IS topology is recalculated to route traffic around the failure.
BFD interaction with graceful restart
If the SR OS router is providing a grace period to an adjacent neighbor and the BFD session associated with that neighbor fails, the behavior is determined by the C-bit values sent by each neighbor.
If both BFD end-points have set their C-bit value, then the graceful restart helper mode is canceled and any routes from that neighbor that are marked as stale are removed from the forwarding table.
If either of the BFD end-points has not set their C-bit value, then the graceful restart helper mode continues.
IS-IS configuration process overview
IS-IS configuration and implementation flow displays the process to provision basic IS-IS parameters.
Configuration notes
This section describes IS-IS configuration restrictions.
General
IS-IS must be enabled on each participating router.
There are no default network entity titles.
There are no default interfaces.
By default, the routers are assigned a level 1/level 2 level capability.
Configuring IS-IS with CLI
This section provides information to configure IS-IS using the command line interface.
IS-IS configuration overview
Router levels
The router’s level capability can be configured globally and on a per-interface basis. The interface-level parameters specify the interface’s routing level. The neighbor capability and parameters define the adjacencies that are established.
IS-IS is not enabled by default. When IS-IS is enabled, the global default level capability is level 1/2 which enables the router to operate as either a level 1, a level 2 router with the associated databases, or both. The router runs separate shortest path first (SPF) calculations for the level 1 area routing and for the level 2 multi-area routing to create the IS-IS routing table.
The level value can be modified on both or either of the global and interface levels to be only level 1-capable, only level 2-capable or level 1 and level 2-capable.
If the default value is not modified on any routers in the area, then the routers try to form both level 1 and level 2 adjacencies on all IS-IS interfaces. If the default values are modified to level 1 or level 2, then the number of adjacencies formed are limited to that level only.
Configuring area address attributes
The area ID, also called an area address, specifies the area address portion of the NET which is used to define the IS-IS area to which the router belongs. At least one area ID should be configured on each router participating in IS-IS. You can configure a maximum of three area IDs per router.
- MD-CLI
configure router isis area-address
- classic
CLI
configure router isis area-id
The area address identifies a point of connection to the network, such as a router interface, and is called a Network Service Access Point (NSAP). The routers in an area manage routing tables about destinations within the area. The Network Entity Title (NET) value is used to identify the IS-IS area to which the router belongs.
NSAP addresses are divided into three parts. Only the Area ID portion is configurable.
-
Set the area ID.
A variable length field between 1 and 13 bytes long. This includes the Authority and Format Identifier (AFI) as the most significant byte and the area ID.
-
Set the system ID.
A six-byte system identification. This value is not configurable. The system ID is derived from the system or router ID.
-
Set the selector ID.
A one-byte selector identification that must contain zeros when configuring a NET. This value is not configurable. The selector ID is always 00.
The following example displays ISO addresses in IS-IS address format:MAC address 00:a5:c7:6b:c4:9049.0011.00a5.c76b.c490.00 IP address: 218.112.14.5 49.0011.2181.1201.4005.00
Interface level capacity
The level capability value configured on the interface level is compared to the level capability value configured on the global level to determine the type of adjacencies that can be established. The default level capability for routers and interfaces is level 1/2.
Potential adjacency displays configuration combinations and the potential adjacencies that can be formed.
Global level | Interface level | Potential adjacency |
---|---|---|
L 1/2 |
L 1/2 |
Level 1 and/or Level 2 |
L 1/2 |
L 1 |
Level 1 only |
L 1/2 |
L 2 |
Level 2 only |
L 2 |
L 1/2 |
Level 2 only |
L 2 |
L 2 |
Level 2 only |
L 2 |
L 1 |
— |
L 1 |
L 1/2 |
Level 1 only |
L 1 |
L 2 |
— |
L 1 |
L 1 |
Level 1 only |
Route leaking
Nokia’s implementation of IS-IS route leaking is performed in compliance with RFC 2966, Domain-wide Prefix Distribution with Two-Level IS-IS. As previously stated, IS-IS is a routing domain (an autonomous system running IS-IS) which can be divided into level 1 areas with a level 2-connected subset (backbone) of the topology that interconnects all of the level 1 areas. Within each level 1 area, the routers exchange link state information. Level 2 routers also exchange level 2 link state information to compute routes between areas.
Routers in a level 1 area typically only exchange information within the level 1 area. For IP destinations not found in the prefixes in the level 1 database, the level 1 router forwards PDUs to the nearest router that is in both level 1/level 2 with the attached bit set in its level 1 link-state PDU.
There are many reasons to implement domain-wide prefix distribution. The goal of domain-wide prefix distribution is to increase the granularity of the routing information within the domain. The routing mechanisms specified in RFC 1195 are appropriate in many situations and account for excellent scalability properties. However, in specific circumstances, the amount of scalability can be adjusted which can distribute more specific information than described by RFC 1195.
Distributing more prefix information can improve the quality of the resulting routes. A well-known property of default routing is that loss of information can occur. This loss of information affects the computation of a route based upon less information which can result in sub-optimal routes.
Basic IS-IS configuration
For IS-IS to operate on the routers, IS-IS must be explicitly enabled, and at least one area address and interface must be configured. If IS-IS is enabled but no area address or interface is defined, the protocol is enabled but no routes are exchanged. When at least one area address and interface are configured, then adjacencies can be formed and routes exchanged.
-
Enable IS-IS (specifying the instance ID of multi-instance IS-IS is to be enabled).
-
Modify the level capability, if necessary, on the global level (default is level-1/2).
-
Define area addresses.
-
Configure IS-IS interfaces.
The following example displays IS-IS default values.
MD-CLI
[ex:/configure router "Base" isis 0]
A:admin@node-2# info detail
## apply-groups
## apply-groups-exclude
admin-state disable
## authentication-keychain
## authentication-key
## authentication-type
csnp-authentication true
psnp-authentication true
advertise-passive-only false
## advertise-router-capability
advertise-tunnel-link false
all-l1isis 01:80:c2:00:00:14
all-l2isis 01:80:c2:00:00:15
authentication-check true
## default-route-tag
ldp-sync true
hello-authentication true
ignore-attached-bit false
ignore-lsp-errors false
ignore-narrow-metric false
iid-tlv false
ipv4-multicast-routing native
ipv4-routing true
ipv6-multicast-routing native
## export-limit
## graceful-restart
entropy-label {alse
override-tunnel-elc false
}sp-lifetime 1200
## multi-topologymaining-lifetime
multicast-import {
ipv4 falseetection false
ipv6 falset-interlevel false
}verload-export-external false
## overloadfalse
## overload-on-boots-tlv false
## prefix-limitndwidth
lsp-refresh {
interval 600nstance false
half-lifetime true false
}uppress-attached-bit false
rib-priority {.0000.0000
high {
## prefix-list
## tag
}
}
flexible-algorithms {
admin-state disable
advertise-admin-group prefer-ag
## flex-algonitial-wait 1000
} spf-second-wait 1000
traffic-engineering-options {
advertise-delay false
ipv6 falsex-wait 5000
## application-link-attributes
} lsp-second-wait 1000
segment-routing {
## apply-groups
## apply-groups-exclude
admin-state disable
adj-sid-hold 15
class-forwarding false
entropy-label true
## export-tunnel-table
## srlb
## tunnel-mtu
tunnel-table-pref 11
adjacency-sid {
allocate-dual-sids false
mapping-server {
admin-state disable
## node-sid-map
}maximum-sid-depth {
} ## override-bmi
segment-routing-v6 {d
## apply-groups
## apply-groups-exclude
admin-state disable
adj-sid-hold 15se
## locator-sid false
## micro-segment-locator
} }
igp-shortcut {atistics {
## apply-groupsfalse
## apply-groups-exclude
admin-state disable
allow-sr-over-srte false
tunnel-next-hop {
family ipv4 {
## apply-groups
## apply-groups-exclude
resolution none
resolution-filter {
rsvp false
sr-te false
}
}
family srv6 {
## apply-groups
## apply-groups-exclude
resolution none
resolution-filter {
rsvp false
sr-te false
}
}
}
}
## interface
level 1 {
## apply-groups
## apply-groups-exclude
## authentication-keychain
## authentication-key
## authentication-type
csnp-authentication true
psnp-authentication true
advertise-router-capability true
database-export-exclude false
default-ipv4-multicast-metric 10
default-ipv6-multicast-metric 10
default-ipv6-unicast-metric 10
default-metric 10
external-preference 160
hello-authentication true
## hello-padding
loopfree-alternate-exclude false
lsp-mtu-size 1492
preference 15
wide-metrics-only false
bier {
admin-state disable
## template
}
}
level 2 {
## apply-groups
## apply-groups-exclude
## authentication-keychain
## authentication-key
## authentication-type
csnp-authentication true
psnp-authentication true
advertise-router-capability true
database-export-exclude false
default-ipv4-multicast-metric 10
default-ipv6-multicast-metric 10
default-ipv6-unicast-metric 10
default-metric 10
external-preference 165
hello-authentication true
## hello-padding
loopfree-alternate-exclude false
lsp-mtu-size 1492
preference 18
wide-metrics-only false
bier {
admin-state disable
## template
}
}
## link-group
## summary-address
classic CLI
A:node-2>config>router>isis# info detail
----------------------------------------------
no system-id
no router-id
level-capability level-1/2
no graceful-restart
no auth-keychain
no authentication-key
no authentication-type
authentication-check
csnp-authentication
no ignore-lsp-errors
no ignore-narrow-metric
lsp-lifetime 1200
lsp-mtu-size 1492
lsp-refresh-interval 600
no export-limit
no export
no import
hello-authentication
psnp-authentication
no traffic-engineering
no reference-bandwidth
no default-route-tag
no disable-ldp-sync
no advertise-passive-only
no advertise-router-capability
no hello-padding
no ldp-over-rsvp
no advertise-tunnel-link
no ignore-attached-bit
no suppress-attached-bit
no iid-tlv-enable
no poi-tlv-enable
no prefix-limit
no loopfree-alternates
no rib-priority high
ipv4-routing
no ipv6-routing
ipv4-multicast-routing native
ipv6-multicast-routing native
no multi-topology
no unicast-import-disable both
no multicast-import both
no strict-adjacency-check
igp-shortcut
shutdown
tunnel-next-hop
family ipv4
resolution disabled
resolution-filter
no rsvp
no sr-te
exit
family ipv6
resolution disabled
resolution-filter
no rsvp
no sr-te
exit
family srv4
resolution disabled
resolution-filter
no rsvp
no sr-te
exit
family srv6
resolution disabled
resolution-filter
no rsvp
no sr-te
exit
exit
exit
timers
lsp-wait 5000 lsp-initial-wait 10 lsp-second-wait 1000
sfp-wait 10000 sfp-initial-wait 1000 sfp-second-wait 1000
exit
level 1
advertise-router-capability
no hello-padding
no lsp-mtu-size
no auth-keychain
no authentication-key
no authentication-type
csnp-authentication
external-preference 160
hello-authentication
no loopfree-alternate-exclude
preference 15
psnp-authentication
no wide-metrics-only
default-metric 10
default-ipv4-multicast-metric 10
default-ipv6-unicast-metric 10
default-ipv6-multicast-metric 10
exit
level 2
advertise-router-capability
no hello-padding
no lsp-mtu-size
no auth-keychain
no authentication-key
no authentication-type
csnp-authentication
external-preference 165
hello-authentication
no loopfree-alternate-exclude
preference 18
psnp-authentication
no wide-metrics-only
default-metric 10
default-ipv4-multicast-metric 10
default-ipv6-unicast-metric 10
default-ipv6-multicast-metric 10
exit
segment-routing
shutdown
adj-sid-hold 15
no export-tunnel-table
no prefix-sid-range
no tunnel-table-pref
no tunnel-mtu
mapping-server
shutdown
exit
exit
no shutdown
Common configuration tasks
To implement IS-IS in your network, you must enable IS-IS on each participating router.
To assign different level to the routers and organize your network into areas, modify the level capability defaults on end systems from level 1/2 to level 1. Routers communicating to other areas can retain the level 1/2 default.
-
Enable IS-IS.
-
Configure global IS-IS parameters (configure area addresses).
-
Configure IS-IS interface-specific parameters.
Configuring IS-IS components
Use the CLI commands displayed in the following subsections to configure IS-IS components.
Enabling IS-IS
IS-IS is disabled by default and must be configured and administratively enabled for the protocol to be active. SR OS also supports multi-instance IS-IS, which allows separate instances of the IS-IS protocol to run independently of the SR OS router.
Use the following command to configure an instance ID for IS-IS instances.
- MD-CLI
configure router isis isis-instance
- classic CLI
configure router isis
Modifying router-level parameters
When IS-IS is enabled, the router operates with both level‑1 and level‑2 routing. The level-capability value can be configured on the global level and also on the interface level. The level-capability value determines which level values can be assigned on the router level or on an interface-basis. To operate as only a level-1 router or only a level-2 router, you must explicitly specify the level number.
-
Level 1 routes only within an area.
-
Level 2 routes to destinations outside an area, toward other eligible level 2 routers.
- MD-CLI
configure router isis level-capability (1|2|1/2)
- classic
CLI
configure router isis level-capability {level-1|level-2|level-1/2}
- MD-CLI
configure router isis level level-number (1|2)
- classic
CLI
configure router isis level (1|2)
The following is an example of level-capability and level configuration.
MD-CLI
[ex:/configure router "Base" isis 5]
A:admin@node-2# info
level-capability 2
level 2 {
...
}
classic CLI
A:node-2>config>router>isis# info
----------------------------------------------
shutdown
level-capability level-2
level 2
...
exit
----------------------------------------------
Configuring ISO area addresses
- MD-CLI
configure router isis area-address
- classic
CLI
configure router isis area-id
The following example shows the router area ID configuration.
MD-CLI
[ex:/configure router "Base" isis 5]
A:admin@node-2# info
...
area-address [49.0180.0001 49.0180.0002 49.0180.0003]
...
}
classic CLI
A:node-2>config>router>isis# info
----------------------------------------------
...
area-id 49.0180.0001
area-id 49.0180.0002
area-id 49.0180.0003
...
----------------------------------------------
Configuring global IS-IS parameters
Commands and command options configured on the global level are inherited at the interface levels. Configurations in the interface and interface-level take precedence over global configurations.
The following example shows a modified global-level configuration.
MD-CLI
[ex:/configure router "Base" isis 5]
A:admin@node-2# info
authentication-key "authkey hash2"
authentication-type password
authentication-check true
level-capability 2
overload-export-external true
traffic-engineering true
area-address [49.0180.0001 49.0180.0002 49.0180.0003]
}
classic CLI
A:node-2>config>router>isis# info
----------------------------------------------
level-capability level-2
area-id 49.0180.0001
area-id 49.0180.0002
area-id 49.0180.0003
authentication-key "auth-key" hash
authentication-type password
overload timeout 90
traffic-engineering
---------------------------------------------
Migration to IS-IS multi-topology
To migrate to IS-IS Multi-Topology (MT) for IPv6, perform the steps described in this topic.
-
Use the following command to enable sending and receiving of IPv6 unicast
reachability information in IS-IS MT TLVs on all the routers that support
MT.
configure router isis multi-topology ipv6-unicast
MD-CLI[ex:/configure router "Base" isis 0] A:admin@node-2# info ... ipv6-routing native multi-topology { ipv6-unicast true ipv4-multicast true } ...
classic CLIA:node-2>config>router>isis# info detail ---------------------------------------------- ... ipv4-routing ipv6-routing native multi-topology ipv6-unicast exit ... ----------------------------------------------
-
Use the following commands to ensure that all routers to be configured for MT
have the IPv6 reachability information required by MT TLVs.
-
Use the following command to configure MT TLVs for IPv6 SPF.
configure router isis ipv6-routing mt
MD-CLI[ex:/configure router "Base" isis 0] A:admin@node-2# info ... ipv6-routing mt multi-topology { ipv6-unicast true ipv4-multicast true } ... ----------------------------------------------
classic CLIA:node-2>config>router>isis# info detail ---------------------------------------------- ... ipv4-routing ipv6-routing mt multi-topology ipv6-unicast exit ... ----------------------------------------------
-
Use the following commands to verify the IPv6 routes for IS-IS.
Configuring IS-IS interfaces
You must configure at least one IS-IS interface for IS-IS to work. There are no default interfaces applied to the router’s IS-IS instance. An interface belongs to all areas configured on a router. Interfaces cannot belong to separate areas.
Configuring interfaces with level capability
Describes how to configure IS-IS interfaces with level capability.
Use the following procedure to configure and enable IP interfaces for IS-IS. You must configure at least one IS-IS interface for IS-IS to work.
-
Use the following command to configure IP interfaces to use for IS-IS.
configure router interface
MD-CLI[ex:/configure router "Base"] A:admin@node-2# info interface "NOK-1-1" { } interface "NOK-1-2" { } interface "NOK-1-3" { } interface "NOK-1-5" { } interface "system" { } interface "to-103" { }
classic CLIA:node-2>config>router# info #-------------------------------------------------- interface "NOK-1-1" no shutdown exit interface "NOK-1-2" no shutdown exit interface "NOK-1-3" no shutdown exit interface "NOK-1-5" no shutdown exit interface "system" no shutdown exit interface "to-103" no shutdown exit #--------------------------------------------------
-
Use the following command to reference the interfaces created in step 1 for IS-IS.
configure router isis interface
MD-CLI[ex:/configure router "Base" isis 0] A:admin@Dut-AC# info ... interface "NOK-1-1" { } interface "NOK-1-2" { } interface "ALA-1-3" { } interface "ALA-1-5" { } interface "system" { } interface "to-103" { }
classic CLIA:node-2>config>router>isis# interface "NOK-1-2" *A:node-2>config>router>isis>if# ...
-
Use the following commands to configure level 1 and level 2 options and the
level-capability for an interface. The level-capability value
determines which level values are used.
configure router isis level configure router isis interface configure router isis interface level-capability configure router isis interface-type
Note: For point-to-point interfaces, only values configured under level 1 are used, regardless of the operational level of the interface.The following example shows global and interface-level configurations.
MD-CLI[ex:/configure router "Base" isis 0] A:admin@node-2# info authentication-key "auth-key= hash2" authentication-type password ipv6-routing native level-capability 2 traffic-engineering true area-address [49.0180.0001 49.0180.0002 49.0180.0003] multi-topology { ipv6-unicast true ipv4-multicast false } interface "ALA-1-2" { level-capability 2 } interface "ALA-1-3" { interface-type point-to-point level-capability 1 } interface "ALA-1-5" { interface-type point-to-point level-capability 1 } interface "system" { } interface "to-103" { } level 1 { wide-metrics-only true } level 2 { wide-metrics-only true }
classic CLIA:node-2>config>router>isis# info ---------------------------------------------- level-capability level-2 area-id 49.0180.0001 area-id 49.0180.0002 area-id 49.0180.0003 authentication-key "auth-key" hash authentication-type password traffic-engineering level 1 wide-metrics-only exit level 2 wide-metrics-only exit interface "system" exit interface "ALA-1-2" level-capability level-2 exit interface "ALA-1-3" level-capability level-1 interface-type point-to-point exit interface "ALA-1-5" level-capability level-1 interface-type point-to-point exit interface "to-103" exit ----------------------------------------------
Configuring a level 1 area
Interfaces are configured in the configure router interface context, as shown in Configuring a level 1 area and the procedure Configuring interfaces with level capability.
The following example displays the command usage to configure a level 1 area.
MD-CLI
[ex:/configure router "Base" isis 0]
A:admin@node-A# info
...
level-capability 1
...
area-address [49.0180.0001 49.0180.0002 49.0180.0003]
...
}
interface "A-B" {
level-capability 1
}
interface "A-C" {
level-capability 1
}
interface "B-A" {
level-capability 1
}
interface "B-C" {
level-capability 1
}
interface "C-A" {
level-capability 1
}
interface "C-B" {
level-capability 1
}
....
classic CLI
A:node-A>config>router>isis# info
----------------------------------------------
level-capability level-1
area-id 49.0180.0001
interface "system"
exit
interface "A-B"
exit
interface "A-C"
exit
----------------------------------------------
A:node-B>config>router>isis# info
----------------------------------------------
level-capability level-1
area-id 49.0180.0002
interface "system"
exit
interface "B-A"
exit
interface "B-C"
exit
----------------------------------------------
A:node-C>config>router>isis# info
#------------------------------------------
echo "ISIS"
----------------------------------------------
level-capability level-1
area-id 49.0180.0003
interface "system"
exit
interface "C-A"
exit
interface "C-B"
exit
----------------------------------------------
Modifying a router’s level capability
In the example shown in Configuring a level 1 area, A, B, and C are configured as level 1 systems. Level 1 systems communicate with other level 1 systems in the same area. In the following example, area A is modified to set the level capability to level 1 and 2, as shown in Configuring a level 1/2 area. Now, the level 1 systems in the area with NET 47.0001 forward PDUs to area A for destinations that are not in the local area.
The following example shows the command usage to change area A from a level 1 system to a level 1/2 system.
MD-CLI
[ex:/configure router "Base" isis 0]
A:admin@node-A# level-capability 1/2
*[ex:/configure router "Base" isis 0]
A:admin@node-A# info
...
level-capability 1/2
...
}
classic CLI
A:node-A>config>router>isis# info
----------------------------------------------
shutdown
level-capability level-1
area-id 49.0180.0001
...
A:node-A>config>router>isis# level-capability level-1/2
*A:node-A>config>router>isis# info
----------------------------------------------
shutdown
area-id 49.0180.0001
...
Configure LFA for IS-IS interfaces
Configure LFA policy maps for interfaces using a route next-hop template
Use the following commands to apply a route next-hop policy template that is configured with the required policies, to all IS-IS prefixes whose primary next hop uses a specific interface. See Application of route next hop policy template to an interface for more information.
- MD-CLI
configure router isis interface loopfree-alternate policy-map route-nh-template configure service vprn isis interface loopfree-alternate policy-map route-nh-template
- classic CLI
configure router isis interface lfa-policy-map route-nh-template configure service vprn isis interface lfa-policy-map route-nh-template
Exclude interfaces from LFA SPF
Use the following commands to exclude an interface in IS-IS or an IS-IS level from an LFA SPF. You can also exclude prefixes from a prefix policy that matches on prefixes or on IS-IS tags, for the router or VPRN service. See Excluding interfaces and prefixes from LFA SPF for more information.
- MD-CLI
configure router isis interface loopfree-alternate exclude configure service vprn isis interface loopfree-alternate exclude
- classic CLI
configure router isis interface loopfree-alternate-exclude configure service vprn isis interface loopfree-alternate-exclude
Configuring IS-IS link groups
IS-IS Link-Groups allows the creation of an administrative grouping of multiple IS-IS member interfaces that should be treated as a common group for ECMP purposes. If the number of operational links in the link-group drops below the operational-member value, then all links associated with that IS-IS link group will have their interface metric increased by the configured offset amounts. As a result, IS-IS will then try to reroute traffic over lower cost paths.
After it is triggered, the higher metric will not be reset to the originally configured IS-IS interface metric values until the number of active interfaces in the link bundle reaches the configured revertive threshold (revert-members).
Prerequisite are the following:
one or more interface members
a configured operational-member (oper-members) value
a configured revertive-member (revert-members) value
configured offset values for the appropriate address families
IS-IS configuration management tasks
This section discusses IS-IS configuration management tasks.
Disabling IS-IS
When you administratively disable the IS-IS protocol instance on the router, the configuration settings are not changed, reset, or removed. Use the following command to disable IS-IS on a router:
- MD-CLI
configure router isis admin-state disable
- classic
CLI
configure router isis shutdown
Removing IS-IS
When you remove the IS-IS protocol instance, the IS-IS configuration reverts to the default settings.
Use the following command to remove the IS-IS configuration:
- MD-CLI
config router delete isis
- classic
CLI
configure router no isis
Modifying global IS-IS configuration
You can modify, disable, or remove global IS-IS configuration without administratively disabling the entities. Changes take effect immediately. Modifying the level capability on the global level causes the IS-IS protocol to restart.
Modifying IS-IS interface configuration
You can modify, disable, or remove interface-level IS-IS configuration without administratively disabling the entities. Changes take effect immediately. Modifying the level capability on the interface causes the IS-IS protocol on the interface to restart.
Use the following command to remove an interface:
- MD-CLI
configure router delete interface
- classic
CLI
configure router no interface
Use the following command to disable an interface:
- MD-CLI
configure router interface admin-state disable
- classic
CLI
configure router interface shutdown
The following example displays interface IS-IS modification command usage. For specific interface configuration and modification examples also see, Configuring a level 1 area and Modifying a router’s level capability.
Configuring authentication using keychains
The use of authentication mechanism is recommended to protect against malicious attack on the communications between routing protocol neighbors. These attacks could aim to either disrupt communications or to inject incorrect routing information into the systems routing table. The use of authentication keys can help to protect the routing protocols from these types of attacks. In addition, the use of authentication keychains provides the ability to configure authentication keys and make changes to them without affecting the state of the routing protocol adjacencies.
To configure the use of an authentication keychain within IS-IS, use the following steps.
Use the following command to configure an authentication keychain. The configured keychain must include at least one valid key entry, using a valid authentication algorithm for the IS-IS protocol.
- MD-CLI
configure system security keychains
- classic CLI
configure system security keychain
- MD-CLI
Associate the configure authentication keychain with IS-IS. Authentication keychains can be used to specify the authentication at the IS-IS global and level contexts, as well as for hello authentication at the interface and interface-level context.
- MD-CLI
configure router isis hello-authentication-keychain
- classic
CLI
configure router isis auth-keychain
- MD-CLI
Use the following command to establish the hello authentication association:
- MD-CLI
configure router isis hello-authentication
- classic
CLI
configure router isis hello-auth-keychain
For a key entry to be valid, it must include a valid key, the current system clock value must be within the begin and end time of the key entry, and the algorithm specified in the key entry must be supported by the IS-IS protocol.
The IS-IS protocol supports the following algorithms:
clear text password (RFC 5304 and RFC 5310 formats)
HMAC-MD5 (RFC 5304 and RFC 5310 formats)
HMAC-SHA-1 (RFC 5310 format)
HMAC-SHA-256 (RFC 5310 format)
The IS-IS key entry may also include the option to determine how the IS-IS protocol encodes the authentication signature. Thebasic command option results in the use of RFC 5304 format. The default or a value of the isis-enhanced command option results in using the RFC 5310 format.
Use the following command to configure the encoding of the IS-IS protocol authentication signature:
- MD-CLI
configure system security keychains keychain bidirectional entry option
- classic
CLI
configure system security keychain direction bi entry
The error handling is described below.
If a keychain exists but there are no active key entries with an authentication type that is valid for the associated protocol then inbound protocol packets are not authenticated and discarded and no outbound protocol packets should be sent.
If keychain exists, but the last key entry has expired, a log entry is raised indicating that all keychain entries have expired. The IS-IS protocol requires that the protocol not revert to an unauthenticated state and requires that the old key is not to be used, therefore, after the last key has expired, all traffic is discarded.
Guidelines for configuring route leaking from level 2 to level 1 areas
IS-IS allows a two-level hierarchy to route PDUs. Level 1 areas can be interconnected by a contiguous level 2 backbone. The level 1 link-state database contains information only about that area. The level 2 link-state database contains information about the level 2 system and each of the level 1 systems in the area. A level 1/2 router contains information about both level 1 and level 2 databases. A level 1/2 router advertises information about its level 1 area toward the other level 1/2 or level 2 (only) routers.
Packets with destinations outside the level 1 area are forwarded toward the closest level 1/2 router which, in turn, forwards the packets to the destination area.
Sometimes, the shortest path to an outside destination is not through the closest level 1/2 router, or, the only level 1/2 system to forward packets out of an area is not operational. Route leaking provides a mechanism to leak level 2 information to level 1 systems to provide routing information about inter-area routes. A level 1 router then has more options to forward packets.
See Configuring route leaking from level 2 to level 1 areas for information about how to configure route leaking.
Configuring route leaking from level 2 to level 1 areas
This topic describes how to configure policies to leak routes from level 2 to level 1.
- Review the guidelines in Guidelines for configuring route leaking from level 2 to level 1 areas.
- In the classic CLI, when configuring policy-options you must use the begin command to enter edit mode and the commit command to save the configuration.
This task describes how to configure policies, including a prefix list and policy statement, to leak routes from level 2 to level 1 areas.
-
Use the commands in the following contexts to configure a policy to leak routes
from level 2 into level 1 areas:
- MD-CLINote: Use the commit command to save the configuration.
- classic CLINote: Use the begin command to enter edit mode for the policy-options configuration and the commit command to save the configuration.
MD-CLI[ex:/configure policy-options] A:admin@node-2# info prefix-list "loops" { prefix 10.1.1.0/24 type longer { } } policy-statement "leak" { entry 10 { from { level 2 prefix-list "loops" } to { level 1 } action { action-type accept } } }
classic CLIA:node-2>config>router>policy-options# info ---------------------------------------------- prefix-list "loops" prefix 10.1.1.0/24 longer exit policy-statement "leak" entry 10 from prefix-list "loops" level 2 exit to level 1 exit action accept exit exit exit ---------------------------------------------
- MD-CLI
-
Use the following command to apply the policy statement created in step 1 to leak routes from level 2 info level 1
systems on the node.
- MD-CLI
configure router isis export-policy
- class
CLI
configure router isis export
MD-CLI[ex:/configure router "Base" isis 0] A:admin@node-A# info authentication-key "auth-key= hash2" authentication-type password ... area-address [49.0180.0001 49.0180.0002 49.0180.0003] authentication-check false export-policy "leak" ...
classic CLIA:node-A>config>router>isis# info ---------------------------------------------- area-id 49.0180.0001 area-id 49.0180.0002 area-id 49.0180.0003 authentication-key "//auth-key" hash authentication-type password no authentication-check export "leak" ... ----------------------------------------------
- MD-CLI
-
After exporting the policy, use the commands in the following context to create
a policy to redistribute external IS-IS routes from level 1 systems into the
level 2 backbone (see Redistributing external IS-IS routers).
- MD-CLI
configure policy-options prefix-list configure policy-options policy-statement entry
- classic
CLI
configure router policy-options prefix-list configure router policy-options policy-statement entry
MD-CLI[ex:/configure policy-options] A:node-AC# info prefix-list "loops" { prefix 10.1.1.0/24 type longer { } } policy-statement "leak" { entry 10 { from { level 2 prefix-list ["loops"] } to { level 1 } action { action-type accept } } } policy-statement "isis-ext" { entry 10 { from { external true } to { level 2 } action { action-type accept } } }
classic CLIA:node-AC>config>router>policy-options# info ---------------------------------------------- prefix-list "loops" prefix 10.1.1.0/24 longer exit policy-statement "leak" entry 10 from prefix-list "loop" level 2 exit to level 1 exit action accept exit exit exit policy-statement "isis-ext" entry 10 from external exit to level 2 exit action accept exit exit exit ----------------------------------------------
- MD-CLI
Redistributing external IS-IS routers
IS-IS does not redistribute level 1 external routes into level 2 by default. You must explicitly apply the policy to redistribute external IS-IS routes. Use the commands in the following context to create and apply a policy to redistribute external IS-IS routes:
- MD-CLINote: Use the commit command to save the configuration.
configure policy-options prefix-list configure policy-options policy-statement entry
- class CLINote: Use the begin command to enter edit mode for the policy-options configuration and the commit command to save the configuration.
configure router policy-options prefix-list configure router policy-options policy-statement entry
See Route policies for more information about creating and using route policies.
The following example shows a policy-statement configuration.
MD-CLI
[ex:/configure policy-options]
A:node-AC# info
prefix-list "loops" {
prefix 10.1.1.0/24 type longer {
}
}
policy-statement "isis-ext" {
entry 10 {
from {
external true
}
to {
level 2
}
action {
action-type accept
}
}
}
policy-statement "leak" {
entry 10 {
from {
level 2
prefix-list ["loops"]
}
to {
level 1
}
action {
action-type accept
}
}
}
classic CLI
A:node-AC>config>router>policy-options# info
----------------------------------------------
prefix-list "loops"
prefix 10.1.1.0/24 longer
exit
policy-statement "leak"
entry 10
from
prefix-list "loops"
level 2
exit
to
level 1
exit
action accept
exit
exit
exit
policy-statement "isis-ext"
entry 10
from
external
exit
to
level 2
exit
action accept
exit
exit
exit
---------------------------------------------
Specifying MAC addresses for all IS-IS routers
Use the following commands to specify a MAC address for all L1 IS-IS routers.
configure router isis all-l1isis
configure service vprn isis all-l1isis
Use the following commands to specify the MAC address for all L2 IS-IS routers.
configure router isis all-l2isis
configure service vprn isis all-l2isis