Redistribution Notes - Tagging

• Tagging provides a way to mark common or similar routes to manipulate later.
• In redistribution scenarios with mutual redistribution on two different routers, any routes that gets redistributed from one route process to another are tagged.
  • When the other router sees those tags on the route, that route to keep from adding non-optimal routes to its routing table.
• Tags can also be used to do other manipulation such as setting higher metrics or changing ADs.

OSPF

R102#show run
...
router ospf 1
log-adjacency-changes
redistribute connected subnets route-map SETTAG
network 192.0.2.0 0.0.0.255 area 0
!
route-map SETTAG permit 100
set tag 55555
...

R101#sh ip route 10.0.0.2
Routing entry for 10.0.0.0/24
Known via "ospf 1", distance 110, metric 20
Tag 55555, type extern 2, forward metric 10
Last update from 192.0.2.102 on Ethernet0/0, 00:00:13 ago
Routing Descriptor Blocks:
* 192.0.2.102, from 192.0.2.102, 00:00:13 ago, via Ethernet0/0
Route metric is 20, traffic share count is 1
Route tag 55555

EIGRP

R102#sh run
...
router eigrp 1
network 192.0.2.0
redistribute connected route-map SETTAG
no auto-summary
!
route-map SETTAG permit 100
set tag 55555
...

R101#sh ip route 10.0.0.2
Routing entry for 10.0.0.0/24
  Known via "eigrp 1", distance 170, metric 409600
  Tag 55555, type external
  Redistributing via eigrp 1
  Last update from 192.0.2.102 on Ethernet0/0, 00:00:14 ago
  Routing Descriptor Blocks:
  * 192.0.2.102, from 192.0.2.102, 00:00:14 ago, via Ethernet0/0
      Route metric is 409600, traffic share count is 1
      Total delay is 6000 microseconds, minimum bandwidth is 10000 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 1
      Route tag 55555

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Corrections are encouraged.