OSPF redistribution Tagging scenario

MrXpert

See attached topology and the given answer. 2 way multipoint redistribution is occurring on routers 2 and 4. Do the tagging numbers and permit/deny statements look right? the aim being to prevent loops using those tags

or is this variation below a legit way of doing it: ?

R2 Config
route-map 1-TO-2, deny, sequence 10
Match clauses:
tag 88
Set clauses:
Policy routing matches: 0 packets, 0 bytes
route-map 1-TO-2, permit, sequence 20
Match clauses:
Set clauses:
tag 77
Policy routing matches: 0 packets, 0 bytes
route-map 2-TO-1, deny, sequence 10
Match clauses:
tag 77
Set clauses:
Policy routing matches: 0 packets, 0 bytes
route-map 2-TO-1, permit, sequence 20
Match clauses:
Set clauses:
tag 88
Policy routing matches: 0 packets, 0 bytes




R4Config

route-map 1-TO-2, deny, sequence 10
Match clauses:
tag 88
Set clauses:
Policy routing matches: 0 packets, 0 bytes
route-map 1-TO-2, permit, sequence 20
Match clauses:
Set clauses:
tag 77
Policy routing matches: 0 packets, 0 bytes
route-map 2-TO-1, deny, sequence 10
Match clauses:
tag 77
Set clauses:
Policy routing matches: 0 packets, 0 bytes
route-map 2-TO-1, permit, sequence 20
Match clauses:
Set clauses:
tag 88
Policy routing matches: 0 packets, 0 bytes

Nate--IRL--

MrXpert wrote: »

or is this variation below a legit way of doing it: ?

I would have approached it like you described in your post, rather than what you had in your picture. Setting Tags per process rather than per router makes much more sense to me.

Nate

Monkerz

To simplify it, you could use the same tag number. There is really no reason to use two different tags in this example, unless its just easier for you to read.

Nate--IRL--

Monkerz wrote: »

To simplify it, you could use the same tag number.

Could you give an example? I can't see how that'd work with Multipoint 2-way redistribution.

Nate

Monkerz

Using the same example, with one simple route-map on both routers:

route-map Redistribution-Filter deny 10
match tag 13
route-map Redistribution-Filter permit 20
set tag 13

Apply the redistribution route-map to both OSPF processes on both routers:

router ospf 1
redistribute ospf 2 subnets route-map Redistribution-Filter
router ospf 2
redistribute ospf 1 subnets route-map Redistribution-Filter



Simply put:

a. R2 will redistribute its OSPF1 routes, as long as they are not tagged with 13, into OSPF2 tagging them with 13, when R4 sees these routes he/she will not redistribute back into OSPF1 because he is denying 13.

b. R2 will redistribute its OSPF2 routes, as long as they are not tagged with 13, into OSPF1 tagging them with 13, when R4 sees these routes he/she will not redistribute back into OSPF2 because he is denying 13.

c. R4 will redistribute its OSPF1 routes, as long as they are not tagged with 13, into OSPF2 tagging them with 13, when R2 sees these routes he/she will not redistribute back into OSPF1 because he is denying 13.

d. R4 will redistribute its OSPF2 routes, as long as they are not tagged with 13, into OSPF1 tagging them with 13, when R2 sees these routes he/she will not redistribute back into OSPF2 because he is denying 13.

Nate--IRL--

Makes sense, a much more elegant solution.

Nate