Administrator Guide

Layer 3 Routing Commands 1291

Default Configuration

The default hop count is 64.

Command Mode

BGP Router Configuration mode, IPv6 Address Family Configuration mode

User Guidelines

The ebgp-multihop parameter is relevant only for external BGP neighbors.

For internal BGP neighbors, the TTL value remains 64 and can’t be modified.

A neighbor can inherit this configuration from a peer template. To make the

update-source config work for external BGP neighbors, ebgp-multihop hop-

count should be configured to a TTL value larger than the default TTL of 1.

Autodetect Interface

When BGP is deployed in an IPv6 data center network, it is desirable to use

IPv6 link local addresses as BGP neighbors. Using link local addresses avoids

the need to assign and manage global IPv6 addresses on interconnect links.

Dell Networking already supports BGP neighbors with link local IPv6

addresses, but it requires that the link local IPv6 address of the neighbor be

configured using the BGP “neighbor” command. Since the link local address

is derived from the switch MAC address, the network administrator needs to

know the MAC address of all the switches deployed in the network, and if one

switch fails and is replaced with a different switch then all the BGP neighbor

switches need to be reconfigured to change the link local address specified in

their neighbor commands.

The IPv6 Link Local Address Auto Detect feature eliminates the need for the

network administrator to configure the link local IPv6 address of every

neighbor. Instead of specifying the link local IPv6 address, the network

administrator can use a special keyword “autodetect” to refer to the link local

IPv6 address of the neighbor. For example: “neighbor autodetect interface

0/21 remote-as 10000”

There are several restrictions to this feature:

The “interface” can only refer to non-multiple access VLAN routing

interfaces. It does not work on tunnels.

Only one “autodetect” neighbor can be configured per interface.

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