Bgp Failover Configuration - Lenovo CN4093 Application Manual

BGP Failover Configuration

1. Define the VLANs.
2. Define the IP interfaces with IPv4 addresses.
CN 4093(config)# interface ip 1 address 200.200.200.1 255.255.255.0 enable
CN 4093(config-ip-if)# exit
CN 4093(config)# interface ip 2 address 210.210.210.1 255.255.255.0 enable
CN 4093(config-ip-if)# exit
442
CN4093 Application Guide for N/OS 8.3
Use the following example to create redundant default gateways for a CN4093 at a
Web Host/ISP site, eliminating the possibility, should one gateway go down, that
requests will be forwarded to an upstream router unknown to the switch.
As shown in Figure 45, the switch is connected to ISP 1 and ISP 2. The customer
negotiates with both ISPs to allow the switch to use their peer routers as default
gateways. The ISP peer routers will then need to announce themselves as default
gateways to the CN4093.
Figure 45. BGP Failover Configuration Example
ISP 1
Peer 1 Router
AS 100
(Primary)
IP:200.200.200.2
Default gateway,
with routes having
shorter AS PATH
IP: 200.200.200.10
On the CN4093, one peer router (the secondary one) is configured with a longer AS
path than the other, so that the peer with the shorter AS path will be seen by the
switch as the primary default gateway. ISP 2, the secondary peer, is configured
with a metric of "3," thereby appearing to the switch to be three router hops away.
For simplicity, both default gateways are configured in the same VLAN in this
example. The gateways could be in the same VLAN or different VLANs
CN 4093(config)# vlan 1
The switch will need an IP interface for each default gateway to which it will be
connected. Each interface must be placed in the appropriate VLAN. These
interfaces will be used as the primary and secondary default gateways for the
switch.
ISP 2
AS 200
GbE Switch Module
announces routes with
metric of "3"
IP: 200.200.200.1
IP: 210.210.210.1
Server 2
BladeCenter
Server 1
IP: 200.200.200.11
Peer 2 Router
(Secondary)
IP:210.210.210.2
Metric = AS path
length (metric of '3') = local
AS repeated 3 times
.