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Forum Replies

  1. Excellent article, Rene. Is this a way to prevent what they call asymmetric routing?

  2. It's mostly used to prevent routing loops or sub-optimal routing paths that are caused by redistribution. Asymmetric routing doesn't have to be a problem...when using IGPs (OSPF / EIGRP) you will mostly see symmetric routing but with BGP, asymmetric routing is likely to occur.

  3. Hello Rene,

    I have intlo0 with ip address of 1.1.1.1/24

    I have access-list 1 permit 1.1.1.1 0.0.0.0 and route map route-map TST permit
    route-map TST
    set tag 222

    match ip address 1
    set tag 111

    and redistribute into ospf from eigrp

    redistribute eigrp 100 subnets route-map TST

    but at the destination router I only see tag 222 for the prefix 1.1.1.1 instead of 111

    as son as I change the access list wild card mask to 0.0.0.255 the destination router sees the correct tag of 111

    Could you please explain this why with wilcard 0.0.0.0 the correct tag is not shown but with 0.0.0.255 the correct tag is shown?

    Best Regards,
    -Rouzbeh

  4. Rouzbeh,
    It looks to me that although your interface address for the loopback is 1.1.1.1, the actual route corresponding to that interface is /24 not /32. It is the route, not the host address that has tags applied to it. Since the 1.1.1.0/24 route is not matched by your access-list 1 statement of 1.1.1.1 0.0.0.0, your tag is not getting applied.

    Here is another way to test this theory. Change your access-list back to what you had originally (1.1.1.1 0.0.0.0), but change your loopback address to 1.1.1.1/32 (1.1.1.1 255.255.255.255), and see whether you now have the tag 111 for 1.1.1.1.

  5. andrew says:

    Nyi,
    Yes, you can do this, but you need to be aware of how the difference in writing a route-map determines whether your conditions are logical ANDs or ORs.

    The following route-map would only act on a route that has all of the tags 10, 20, and 30

    route-map TAG deny 10
     match tag 10
     match tag 20
     match tag 30

    Whereas, the following route-map would act on a route that has any of the tags 10, 20 or 30

    route-map TAG deny 10
     match tag 10 20 30

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