Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 536)

AS_PATH:
2 2001:db8::/64 2001:ab::1 100 0 BI
AS_PATH: 65000 65001
3 2007:7002:17::/64 2071:34::1 0 100 0 BE
AS_PATH: 60750
4 2007:7002:17::/64 2071:33::1 0 100 0 I
AS_PATH: 60750
The first lookup results in an IBGP route, to network 2001:ab::1/128
device# show ipv6 route 2001:ab::1
Type Codes - B:BGP C:Connected I:ISIS L:Local O:OSPF R:RIP S:Static
BGP Codes - i:iBGP e:eBGP
OSPF Codes - i:Inter Area 1:External Type 1 2:External Type 2
Type IPv6 Prefix Next Hop Router Interface Dis/Metric Uptime
Bi 2001:ab::1/128 fe80::768e:f8ff:fef9:7d80
Since the route to 2001:ab::1/128 is not an IGP route, the device cannot reach the next hop through
IPv6, and so cannot use the BGP4+ route. In this case, since recursive next-hop lookups are enabled,
the device next performs a lookup for the 2001:ab::1’s next-hop gateway, 2116:21:16::2.
device# show ipv6 bgp route 2001:ab::1/128
Number of BGP Routes matching display condition : 1
Status A:AGGREGATE B:BEST b:NOT-INSTALLED-BEST C:CONFED_EBGP D:DAMPED
E:EBGP H:HISTORY I:IBGP L:LOCAL M:MULTIPATH m:NOT-INSTALLED-MULTIPATH
S:SUPPRESSED F:FILTERED s:STALE
Prefix Next Hop MED LocPrf Weight Status
1 2001:ab::1/128 2116:21:16::2 1 100 0 BI
AS_PATH:
The next-hop IP address for 2001:ab::1 is not an IGP route, which means the BGP4+ route destination
still cannot be reached through IPv6. The recursive next-hop lookup feature performs a lookup on the
next-hop gateway for 2116:21:16::2
device# show ipv6 route 2116:21:16::2
Type Codes - B:BGP C:Connected I:ISIS L:Local O:OSPF R:RIP S:Static
BGP Codes - i:iBGP e:eBGP
OSPF Codes - i:Inter Area 1:External Type 1 2:External Type 2
Type IPv6 Prefix Next Hop Router Interface Dis/Metric Uptime
O 2116:21:16::/64 fe80::768e:f8ff:fef9:7d80
ve 40 110/20 4h36m
This lookup results in an IGP route that is an OSPF route. As a result, the BGP4+ route destination is
now reachable through IGP, which means the BGP4+ route can be added to the IPv6 route table. The
IPv6 route table with the BGP4+ route is shown here.
device(config-vif-40)# show ipv6 route 2001:db8::/64
Type Codes - B:BGP C:Connected I:ISIS L:Local O:OSPF R:RIP S:Static
BGP Codes - i:iBGP e:eBGP
OSPF Codes - i:Inter Area 1:External Type 1 2:External Type 2
Type IPv6 Prefix Next Hop Router Interface Dis/Metric Uptime
Bi 2001:db8::/64 fe80::768e:f8ff:fef9:7d80
ve 40 200/0 1h54m
The device can use this route because it has an IPv6 route to the next-hop gateway. Without recursive
next-hop lookups, this route would not be in the IPv6 route table.
Using the IPv6 default route as a valid next-hop for a BGP4+ route
By default, the device does not use a default route to resolve a BGP4+ next-hop route. If the IPv6
route lookup for the BGP4+ next-hop does not result in a valid IGP route (including static or direct
routes), the BGP4+ next-hop is considered to be unreachable and the BGP4+ route is not used.
Using the IPv6 default route as a valid next-hop for a BGP4+ route
536 FastIron Ethernet Switch Layer 3 Routing Configuration Guide
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