[c-nsp] Strange SSH lag with ACL applied

Andy Saykao andy.saykao at staff.netspace.net.au
Wed Jan 6 20:02:48 EST 2010


Hi All,
 
I have what seems like a trivial problem but can't figure out what's
causing it.
 
I am trying to SSH from Host A (210.15.210.x) to Host B (203.12.53.x).
Host B is in VLAN2 and there's an ACL on VLAN2 that denies external IP's
from accessing it.
 
What I'm finding is that when I apply the ACL (VLAN2-FILTER-OUT ) to
VLAN2, it takes a very long time for the SSH login promtp to appear. If
I remove the ACL on VLAN2, the SSH prompt is instantaneous. What's going
on with my ACL??? Why the lag for the SSH prompt to appear?
 
interface Vlan2
 ip address 203.12.53.aaa 255.255.255.224
 ip access-group VLAN2-FILTER-OUT out
 no ip redirects
 no ip mroute-cache
 ip ospf priority 15
 load-interval 30
 tag-switching ip
!
ip access-list extended VLAN1-FILTER-OUT
 permit ip host 203.10.110.x host 203.12.53.x
 permit ip host 203.10.110.y host 203.12.53.x
 permit ip host 203.10.110.z host 203.12.53.x
 permit ip 172.16.50.0 0.0.0.255 host 203.12.53.x
 permit ip 172.16.51.0 0.0.0.255 host 203.12.53.x
 permit ip 203.17.103.0 0.0.0.255 host 203.12.53.x
 permit ip 203.17.101.0 0.0.0.255 host 203.12.53.x
 permit ip 210.15.210.0 0.0.0.255 host 203.12.53.x
 permit ip 203.17.96.0 0.0.0.255 host 203.12.53.x
 permit ip 203.17.102.0 0.0.0.255 host 203.12.53.x
 permit ip 172.16.9.0 0.0.0.255 host 203.12.53.x
 deny   ip any host 203.12.53.x
 permit ip any any

 
Interestingly enough when I "permit ip any" to access Host B as the very
first line in the ACL, the SSH prompt is instantaneous. 
 
permit ip any host 203.12.53.x log
 
I even tried permiting Host A as the very first line in the ACL like so,
but no joy.
 
permit ip host 210.15.210.x host 203.12.53.x log
 
Any ideas???
 
Thanks.
 
Andy


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