BGP - prefix-list vs Access-list filtering

From: MASK (afaqk@xxxxxxxxxxxxxx)
Date: Tue Feb 12 2002 - 07:18:20 GMT-3


   
Hello fellows,

How does the BGP advertise the prefix associated with
a loopback inteface?

I configured a loopback with "170.17.7.7/24", and then
redistributed the connnected route, but in the bgp
table it always appears as 170.17.0.0/24, why not as
170.17.7.0/24?

then I tried filtering with a route-map:

router bgp xxx
redistribute connected route-map mymap out

route-map mymap permit 10
match ip address 101

access-list 101 permit ip host 170.17.7.0 host
255.255.255.0

then on the neighbor, i do see that route(not others -
thats ok), but how did that ACL matched with that
route, 170.17.0.0/24 ...!!

Is there any difference when we use, prefix-list under
*route-map* than using access-lists, because I see
that you have to have a "set" clause for route-map
action to take place in case of prefix-list, i dont
understand why that does'nt happen in case of
acces-lists.

i.e.,

route-map mymap1 permit 1
match ip address 101
/* updates permitted/denied based on ACL permit or
deny */

but
route-map mymap1 permit 1
match ip address prefix-list mylist
set weight 100 <<-- always requires that "set" clause

anyone can help out??

Thx
Mask



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