Services over Ethernet with DHCP client

When configuring services over an Ethernet-based router interface that is enabled as a DHCP client, the IP address is dynamically allocated by the DHCP server that the DHCP client communicates with. See DHCP client and Router interface command reference for information about configuring the DHCP client on a router interface.

The IP address allocated by the DHCP server may not be the same address each time the DHCP client issues a DHCP discovery or request message. In any case, the value of the address is not typically known and establishing services over the interface needs to account for this discovered IP address.

Consider the following points when setting up a service over an Ethernet-based router interface.

  • SDP configurations cannot be made from other nodes to the local node. The potentially changing and unknown IP address inhibits the static configuration that is needed to manually configure SDPs.

  • T-LDP signaling sessions cannot be established toward the local node because the potentially changing and unknown IP address inhibits the static configuration of T-LDP sessions toward the interface.

  • BGP sessions cannot be established toward the local node because the potentially changing and unknown IP address inhibits the static configuration of BGP sessions toward the interface.

  • BGP sessions from the local node to peers where MP-BGP and BGP routing is required for services must use the DHCP client IP address as the source IP address for these sessions. Operators must use the router interface name when configuring the BGP local address. For information about configuring the BGP local address, see Using a router interface address as the BGP local address. When the local-address command is configured with the DHCP client interface, BGP sets the source IP address of session packets to the IP address learned by the DHCP client from the DHCP server.

  • BGP far-end peering nodes to the local node must be configured with the dynamic-neighbor command using an IP address range that matches the possible DHCP client addresses on the local node. This allows the IP address assigned by the DHCP server to the DHCP client to dynamically change and re-establish BGP sessions to the same far-end peering node. For information about the dynamic-neighbor command, see the 7450 ESS, 7750 SR, 7950 XRS, and VSR Classic CLI Command Reference Guide.

  • Only services that use auto-bind or auto-gre-sdp can operate over a router interface enabled as a DHCP client. The 7705 SAR-Hm series supports MP-BGP-based VPRN services with auto-bind and BGP-VPLS and BGP-VPWS with auto-gre-sdp.

  • Router interfaces that are enabled as DHCP clients enabled do not support the following services:

    • Layer 2 services that use T-LDP signaling

    • Layer 3 services that do not use auto-bind