Configuration Guide User guide

FastIron Configuration Guide 1373
53-1002494-02
Optional BGP4 configuration tasks
The route to the next-hop gateway is a BGP route, not an IGP route, and thus cannot be used to
reach 240.0.0.0/24. In this case, the Layer 3 switch tries to use the default route, if present, to
reach the subnet that contains the BGP route next-hop gateway.
Example when recursive route lookups are enabled
When recursive next-hop lookups are enabled, the Layer 3 switch recursively looks up the next-hop
gateways along the route until the Layer 3 switch finds an IGP route to the BGP route destination.
Here is an example.
The first lookup results in an IBGP route, to network 102.0.0.0/24.
Since the route to 102.0.0.1/24 is not an IGP route, the Layer 3 switch cannot reach the next hop
through IP, and thus cannot use the BGP route. In this case, since recursive next-hop lookups are
enabled, the Layer 3 switch next performs a lookup for 102.0.0.1 next-hop gateway, 10.0.0.1.
Brocade#show ip route 102.0.0.1
Total number of IP routes: 37
Network Address NetMask Gateway Port Cost Type
102.0.0.0 255.255.255.0 10.0.0.1 1/1 1 B
Brocade#show ip route 240.0.0.0/24
Total number of IP routes: 37
Network Address NetMask Gateway Port Cost Type
0.0.0.0 0.0.0.0 10.0.0.202 1/1 1 S
Brocade#show ip bgp route
Total number of BGP Routes: 5
Status A:AGGREGATE B:BEST b:NOT-INSTALLED-BEST C:CONFED_EBGP D:DAMPED
H:HISTORY I:IBGP L:LOCAL M:MULTIPATH S:SUPPRESSED
Prefix Next Hop Metric LocPrf Weight Status
1 0.0.0.0/0 10.1.0.2 0 100 0 BI
AS_PATH: 65001 4355 701 80
2 102.0.0.0/24 10.0.0.1 1 100 0 BI
AS_PATH: 65001 4355 1
3 104.0.0.0/24 10.1.0.2 0 100 0 BI
AS_PATH: 65001 4355 701 1 189
4 240.0.0.0/24 102.0.0.1 1 100 0 BI
AS_PATH: 65001 4355 3356 7170 1455
5 250.0.0.0/24 209.157.24.1 1 100 0 I
AS_PATH: 65001 4355 701
Brocade#show ip route 102.0.0.1
Total number of IP routes: 38
Network Address NetMask Gateway Port Cost Type
102.0.0.0 255.255.255.0 10.0.0.1 1/1 1 B
AS_PATH: 65001 4355 1