RIP AD filtering

hi

see these examples please,

1-

access-list 1 permit host 1.1.1.1

!

router rip




 distance 255 0.0.0.0 255.255.255.255 1


2-

access-list 2 permit 1.1.1.1

!

router rip




 distance 255 2.2.2.2 0.0.0.0 2


3- 

router rip

  distance 255 1.1.1.0 0.0.0.255

 

 

can someone please tell me what is the different  between these all ?

 

 

 

Comments

  • Here’s my best explanation

     

    #1 links the AD to an ACL, very straightforward.  If the host 1.1.1.1 generates a RIB entry
    then he/she will be assigned an AD of 255

    #2 uses the distance command to say if the host 2.2.2.2
    receives a prefix from host 1.1.1.1 then assign the AD of 255.

    #3 is similar to #1 in the context that it uses the
    prefix and mask as the source and assigns an AD to it.  #3 says if a prefix from 1.1.1.0 0.0.0.255 is
    received then assign it the AD of 255.

     

     

    I might be off but that is my explanation.

  • Hi,

    The address after distance value denotes the source of the routing update. In this case, the first is least specific which tells the local router set distance for any sources of update. The second is most specific as it tells the local router just to add the AD for 2.2.2.2 source. Lastly, if the source of update is under the 1.1.1.0/24 network, it will apply AD values in the routing prefixes coming from them. Keep in mind that there is no ACL in the last statement means that it adds the given AD value for all the updates from that particular source.

    HTH

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