BigIron RX Series Configuration Guide
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53-1001810-01
Enabling next-hop recursion
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Example when recursive route lookups are enabled
When recursive next-hop lookups are enabled, the device recursively looks up the next-hop
gateways along the route until the device finds an IGP route to the BGP route’s 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 device 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 device next performs a lookup for 102.0.0.1’s next-hop gateway, 10.0.0.1.
The next-hop IP address for 102.0.0.1 is not an IGP route, which means the BGP route’s destination
still cannot be reached through IP. The recursive next-hop lookup feature performs a lookup on
10.0.0.1’s next-hop gateway:
This lookup results in an IGP route. In fact, this route is a directly-connected route. As a result, the
BGP route’s destination is now reachable through IGP, which means the BGP route is eligible for
installation in the IP route table. Here is the BGP route in the IP route table.
BigIron RX# 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
BigIron RX# show ip route 102.0.0.1
Total number of IP routes: 38
Network Address Gateway Port Cost Type
102.0.0.0 10.0.0.1 1/1 1 B
AS_PATH: 65001 4355 1
BigIron RX# show ip bgp route 102.0.0.0
Number of BGP Routes matching display condition : 1
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
1 102.0.0.0/24 10.0.0.1 1 100 0 BI
AS_PATH: 65001 4355 1
BigIron RX# show ip route 10.0.0.1
Total number of IP routes: 38
Network Address Gateway Port Cost Type
10.0.0.0 0.0.0.0 1/1 1 D
AS_PATH: 65001 4355 1
BigIron RX# show ip route 240.0.0.0/24
Total number of IP routes: 38
Network Address Gateway Port Cost Type
240.0.0.0 10.0.0.1 1/1 1 B
AS_PATH: 65001 4355 1
Summary of Contents for Brocade DCX
Page 40: ...xl BigIron RX Series Configuration Guide 53 1001810 01 ...
Page 72: ...lxxii BigIron RX Series Configuration Guide 53 1001810 01 ...
Page 88: ...16 BigIron RX Series Configuration Guide 53 1001810 01 Searching and filtering output 1 ...
Page 300: ...228 BigIron RX Series Configuration Guide 53 1001810 01 Displaying IP information 7 ...
Page 318: ...246 BigIron RX Series Configuration Guide 53 1001810 01 Deploying a LAG 8 ...
Page 418: ...346 BigIron RX Series Configuration Guide 53 1001810 01 SuperSpan 12 ...
Page 482: ...410 BigIron RX Series Configuration Guide 53 1001810 01 MRP CLI example 14 ...
Page 506: ...434 BigIron RX Series Configuration Guide 53 1001810 01 Displaying VSRP information 15 ...
Page 582: ...510 BigIron RX Series Configuration Guide 53 1001810 01 Viewing Layer 2 ACLs 20 ...
Page 634: ...562 BigIron RX Series Configuration Guide 53 1001810 01 Troubleshooting ACLs 21 ...
Page 642: ...570 BigIron RX Series Configuration Guide 53 1001810 01 Trunk formation 22 ...
Page 746: ...674 BigIron RX Series Configuration Guide 53 1001810 01 Displaying RIP filters 24 ...
Page 808: ...736 BigIron RX Series Configuration Guide 53 1001810 01 Displaying OSPF information 25 ...
Page 938: ...866 BigIron RX Series Configuration Guide 53 1001810 01 Displaying MBGP information 27 ...
Page 950: ...878 BigIron RX Series Configuration Guide 53 1001810 01 Using secure copy 28 ...
Page 988: ...916 BigIron RX Series Configuration Guide 53 1001810 01 Clearing IS IS information 29 ...
Page 1054: ...982 BigIron RX Series Configuration Guide 53 1001810 01 Sample 802 1x configurations 33 ...
Page 1108: ...1036 BigIron RX Series Configuration Guide 53 1001810 01 sFlow 39 ...
Page 1190: ...1118 BigIron RX Series Configuration Guide 53 1001810 01 Displaying RIPng information 44 ...
Page 1270: ...1198 BigIron RX Series Configuration Guide 53 1001810 01 Displaying ACLs 47 ...
Page 1310: ...1238 BigIron RX Series Configuration Guide 53 1001810 01 Displaying OSPFv3 information 48 ...
Page 1382: ...1310 BigIron RX Series Configuration Guide 53 1001810 01 Commands That Require a Reload D ...
Page 1435: ...BigIron RX Series Configuration Guide 1363 53 1001810 01 VSRP E ...
Page 1436: ...1364 BigIron RX Series Configuration Guide 53 1001810 01 VSRP E ...