07-05-2005 01:20 AM - edited 03-03-2019 09:57 AM
Hi,I want to control the router only receive the specific routes which are 199.172.1.0/24, 199.172.4.0/24, 199.172.5.0/24. I can use the standard access-list: access-list 1 permit 199.172.0.0 0.0.5.0 to fulfill the mission. But I don't know how to fulfill it well with prefix-list? Who can tell me how to do it with prefix-list? Thanks a lot.
Sincerely
07-06-2005 01:25 AM
Who can give me a help about the issue? Thanks a lot!!!
07-06-2005 02:11 AM
Hi,
I assume that you are asking about eBGP neighbor configuration:
Example:
router bgp
network x.y.z.0 mask 255.255.255.0
neighbor 10.10.10.10 remote-as
neighbor 10.10.10.10 prefix-list ABC in
exit
ip prefix-list ABC seq 5 permit 199.172.1.0/24
ip prefix-list ABC seq 10 permit 199.172.4.0/24
ip prefix-list ABC seq 15 permit 199.172.5.0/24
end
Regards
Krishnamurthy Suresh
07-06-2005 02:13 AM
ip prefix-list PREFIX seq 5 permit 199.172.1.0/24
ip prefix-list PREFIX seq 10 permit 199.172.4.0/24
ip prefix-list PREFIX seq 15 permit 199.172.5.0/24
If you want to use only 1 command line then the most specific match would be using a /21 mask for the prefix 199.172.0.0. Since it's not like wild-card mask so I believe this is the most specific match.
07-06-2005 02:18 AM
I believe that you are using bgp.
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00801310cb.shtml
regards,
-amit singh
07-06-2005 02:10 AM
The prefix-list will not allow you to set discontiguous bits like the ACL does. The best you could do in this scenario is to permit a /21 that would include 199.172.0.0 to 199.172.7.0 as follow:
ip prefix-list test seq 5 permit 199.172.0.0/21
If only want to allow the 3 subnets you mentioned then you need to use an ACL.
Hope this helps,
07-06-2005 02:11 AM
Hi,
Try those :
ip prefix-list mylist seq 5 permit 199.172.1.0/24
ip prefix-list mylist seq 10 permit 199.172.4.0/24
ip prefix-list mylist seq 15 permit 199.172.5.0/24
or
ip prefix-list mylist seq 5 permit 199.172.1.0/24
ip prefix-list mylist seq 10 permit 199.172.4.0/23 le 24
The 199.172.0.0/21 is an exact match, it won't do the job.
Thanks,
Jawad
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