Cisco Catalyst 4500 series Administration Manual page 954

About Policy-Based Routing
set default ip next-hop
set default interface
If both the set ip next-hop and set ip next-hop recursive commands are present in the same route-map
statement, the next-hop set command is applied.
If the set ip next-hop command is not available then the set ip next-hop recursive command is applied.
If the set ip recursive-next-hop and the set interface command are not present, then the packet is routed
using the default routing table; it is not dropped. If the packet is required to be dropped, use the set
next-hop recursive command followed by a set interface null0 configuration command.
Load balancing with recursive next-hop
If multiple equal-cost routes to the subnet have been configured by the set ip next-hop recursive
command, load balancing will occur only if all the adjacencies to the routes are resolved. If any of the
adjacencies have not been resolved, then load balancing will not happen and only one of the routes whose
adjacency is resolved will be used. If none of the adjacencies are resolved, then packets will be processed
in software, resulting in at least one of the adjacencies to be resolved and programmed in hardware. PBR
relies on routing protocols or other means to resolve all adjacencies and make load balancing happen.
PBR Route-Map Processing Logic Example
Consider a route-map called rm-test defined as follows:
!
•
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
40-4
access-list 101 permit tcp host 61.1.1.1 host 133.3.3.1 eq 101
access-list 102 deny
access-list 2102 permit tcp host 61.1.1.1 host 133.3.3.1 eq 102
access-list 104 deny
access-list 2104 permit tcp host 61.1.1.1 host 133.3.3.1 eq 104
access-list 105 permit tcp host 61.1.1.1 host 133.3.3.1 eq 105
route-map rm-test permit 21
match ip address 101
set ip next-hop 21.1.1.1
!
route-map rm-test permit 22
match ip address 102
set ip next-hop 22.2.2.1
!
route-map rm-test permit 23
match ip address 101 2102
set interface vlan23
!
route-map rm-test deny 24
match ip address 104
set ip next-hop 24.4.4.1
route-map rm-test deny 25
match ip address 105
set ip next-hop 25.5.5.1
!
route-map rm-test permit 26
match ip address 2104
set ip next-hop 26.6.6.1
TCP packet from 61.1.1.1 to 133.3.3.1 with destination port 101
– Matches ACL 101 in sequence #21.
tcp host 61.1.1.1 host 133.3.3.1 eq 102
tcp host 61.1.1.1 host 133.3.3.1 eq 104
Chapter 40 Configuring Policy-Based Routing
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