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DES-7200 Configuration Guide Chapter 2 Configuring BGP IP VPN
2-32
DES-7200(config-router)# neighbor
ebgp-peer-address update-source
interface-name
Specify the device to use the loopback address to
set up a neighbor relation with the EBGP peer.
DES-7200(config-router)# neighbor
ebgp-peer-address ebgp-multihop
Configure multi-hop attributes.
DES-7200(config-router)#address-fa
mily vpnv4
Enter the BGP VPN address family configuration
mode.
DES-7200(config-router-af)# neighbor
ebgp-peer-address activate
Enable the VPN route exchange with the peer.
DES-7200(config-router-af)# exit
Quit the BGP VPN address family.
DES-7200(config-router)#
address-family ipv4
Enter the BGP IPv4 address family configuration
mode.
DES-7200(config-router-af)# no
neighbor
ebgp-peer-address activate
Disable the IPv4 route exchange.
DES-7200(config-router)# show
running-config
View all configuration information.
Caution
The exchange of IPv4 routes is not required in a multi-hop MP-EBGP session.
At least the routes of the two addresses used to set up the BGP session
should be avoided. Otherwise, a PE has two routes to the PE in another AS.
One route is advertised by the ASBR in the local AS and the other is by the
multi-hop EBGP session. According to BGP specifications, the EBGP route
has a higher priority over the IGBP route by default. As a result, the BGP
module chooses the route advertised by the multi-hop BGP and this results in
the continued flapping of routes on the PE to the PE in another AS. The VPN
routes are thus not reachable.
# Consider an example to set up a multi-hop EBGP session.
DES-7200# configure terminal
DES-7200(config)# router bgp 1
DES-7200(config-router)# neighbor 1.1.1.1 remote-as 2
DES-7200(config-router)# neighbor 1.1.1.1 update-source loopback 0
DES-7200(config-router)# neighbor 1.1.1.1 ebgp-multihop
DES-7200(config-router)# address-family vpnv4
DES-7200(config-router-af)# neighbor 1.1.1.1 activate
DES-7200(config-router-af)# exit