Example when recursive route lookups are disabled, Example when recursive route lookups are enabled – Brocade Virtual ADX Switch and Router Guide (Supporting ADX v03.1.00) User Manual
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Brocade Virtual ADX Switch and Router Guide
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Enabling next-hop recursion
8
Example when recursive route lookups are disabled
The output here shows the results of an unsuccessful next-hop lookup for a BGP4 route. In this
case, next-hop recursive lookups are disabled. This example is for the BGP4 route to network
10.0.0.0/24.
In this example, the device cannot reach 10.0.0.0/24, because the next-hop IP address for the
route is an IBGP route instead of an IGP route, and is considered unreachable by the device. The IP
route table entry for the next-hop gateway for the BGP4 route’s next-hop gateway (10.0.0.1/24) is
shown here.
.
Since the route to the next-hop gateway is a BGP4 route, and not an IGP route, it cannot be used to
reach 10.0.0.0/24. In this case, the device tries to use the default route, if present, to reach the
subnet that contains the BGP4 route next-hop gateway.
Example when recursive route lookups are enabled
When recursive next-hop lookups are enabled, the device continues to look up the next-hop
gateways along the route until the device finds an IGP route to the BGP4 route destination.
Virtual ADX# 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
10.0.0.0/24 10.0.0.1 1
100
0
BI
AS_PATH: 65001 4355 1
3
10.0.0.0/24 10.1.0.2
0
100
0
BI
AS_PATH: 65001 4355 701 1 189
4
10.0.0.0/24 10.0.0.1
1
100
0
I
AS_PATH: 65001 4355 3356 7170 1455
5
10.0.0.0/24
10.157.24.1 1
100
0
I
AS_PATH: 65001 4355 701
Virtual ADX# show ip route 10.0.0.1 hw | longer
Total number of IP routes: 37
Start index: 1 B:BGP Be:EBGP Bi:IBGP D:Connected R:RIP S:Static
O:OSPF IA:Inter area IR:Intra area E1:External type 1 E2:External type 2
(N): Don't advertise *:Candi-default
Destination
NetMask
Gateway
Port
Cost
Type
--------------------------------------------------------------------------
1 10.0.0.0
255.255.255.0
10.0.0.1
1/1
1
B
Virtual ADX# show ip route 10.0.0.0/24 hw | longer
Total number of IP routes: 37
Start index: 1 B:BGP Be:EBGP Bi:IBGP D:Connected I:ISIS S:Static
O:OSPF IA:Inter area IR:Intra area E1:External type 1 E2:External type 2
(N): Don't advertise *:Candi-default
Destination
NetMask
Gateway
Port
Cost
Type
--------------------------------------------------------------------------
1
0.0.0.0
255.255.255.0
10.0.0.201
1/1
1
S