01-23-2012 08:31 AM - edited 03-04-2019 02:59 PM
Good morning, I need to configure an acl that blocks telnet access from an internet-facing router.
I think I want to do something like this:
access-list 102 deny tcp any any eq telnet
But I read a single deny entry will have the effect of implicitly denying all traffic not explicitly permitted.
How would i write this acl to only deny telnet access from the open internet but continue to allow everything else?
Thanks,
Brian
Solved! Go to Solution.
01-23-2012 08:39 AM
access-list 102 deny tcp any any eq telnet
access-list 102 permit ip any any
01-23-2012 08:39 AM
access-list 102 deny tcp any any eq telnet
access-list 102 permit ip any any
01-23-2012 10:43 AM
Hi - this is interesting and I'm just learning about ACL's for my CCNA test.
Would this ACL be applied on the internet router's public side WAN interface like this. My example uses serial 0/0 as the public interface on this router.
conf t
interface serial 0/0
ip access-group 102 in
01-23-2012 10:52 AM
Patrick
Yes that access list would logically be applied inbound on the router's internet facing interface. The result would be that any attempt to telnet to any address inside the network, including any address on the internet router, would be denied and all other traffic would be permitted.
HTH
Rick
01-23-2012 11:04 AM
Thanks Guys,
I tried to picture this as if I'm a tech inside the network, and I need all of my internal subnets to have telnet access to the router, but I want to block all outside traffic from telnetting in.
Thank you for the info!
01-23-2012 11:16 AM
access-list 102 permit tcp [local_subnet] any eq telnet
access-list 102 deny tcp any any eq telnet
access-list 102 permit ip any any
01-23-2012 10:52 AM
Yes, please refer to:
Regards,
Edison
01-23-2012 11:51 AM
Thank you i applied this acl accordingly it appears to be working.
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