I jut recently got to use a route map for the first time, pretty cool. When I was researching this issue I came across prefix lists, access-lists, and route maps. I know what access-lists do but what is the difference between all three of them. They seem to do the same thing so why use one instead of the other?
Depending on what you wanted to achieve, you would use either an access-list or a prefix list to specify traffic.
For example, if you wanted to specify the ip network 22.214.171.124 with an access list you could use:-
access-list 1 permit 126.96.36.199 0.0.0.0 and with a prefix list you could use:-
ip prefix-list name permit 188.8.131.52/16
Depending on how your mind works you can use either. prefix-lists are used quite heavily in bgp configurations. Prefix lists can also get a little complex, where you can say:-
ip prefix-list name permit 184.108.40.206/16 ge 17 le 24
Which would mean anything in the 220.127.116.11/16 network with a mask greater than 17 bits, but less than 24 bits.
I personally prefer to use access-list, given the choice.
A route-map is set of conditions applied to redistribution in a routing protocol. This is the command ou use where you want to apply access-lists and/or prefix lists to routing policy.
access-list 1 permit 18.104.22.168 0.0.255.255
ip prefix-list name permit 22.214.171.124/16
route-map example permit 10
match ip address 1
match ip address prefix name
redistribute static metric 3 route-map example
At the end of a route map is an explicit deny all - just like an access list. The access-list 1 is used to specify the network 126.96.36.199/16 and the prefix list is used to specify the network 188.8.131.52/16.
Then the route-map says to match any ip addresses that conform with the access-list or the prefix-list will be permitted. This is then applied when redistributing static routes into rip (in this example) and given a metric of 3.
In the route-map statements you can also have a choice of match-all or match-any, meaning that the route has to match all of the conditions in the route map, or any of them.
So, to summerise:-
Access-lists - used to specify traffic
Prefix-lists - used to specify traffic
Route-maps - used to set conditions for route redistribution
Hi everyone, I would like to thank you in advance for any help you can provide a newcomer like myself!
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