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OpenDNS Access-list

Posted on 2015-01-26
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Last Modified: 2015-02-18
I have the following access-list on a Layer 3 switch to allow access to OpenDNS for a specific group of PCs.
When I test by doing a DNS lookup, it fails. I can see the number of hits going out increasing but the replies do not get any hits.
I did a Wireshark capture from our Firewall to make sure it was not the cause of the problem by denying the reply traffic back in but it does allow it and then gets dropped by the switch (I am guessing) which sends an ICMP unreachable back to OpenDNS. Do I can see the DNS query to OpenDNS, the reply from open DNS and then the ICMP unreachable from the switch which makes me think the switch is the one dropping the returned traffic.

Can anyone see anything wrong with the following access-list that might be causing the traffic to be blocked?

Extended IP access list PCL_Access_In
    20 permit udp 192.168.95.0 0.0.0.255 host 208.67.220.220 eq domain log (473 matches)
    30 permit udp 192.168.95.0 0.0.0.255 host 208.67.222.222 eq domain log (648 matches)
Extended IP access list PCL_Access_Out
    20 permit udp host 208.67.220.220 192.168.95.0 0.0.0.255 eq domain log
    30 permit udp host 208.67.222.222 192.168.95.0 0.0.0.255 eq domain log
      
interface Vlan10
 description PCL_Machines
 ip address 192.168.95.1 255.255.255.0
 ip access-group PCL_Access_In in
 ip access-group PCL_Access_Out out


Thanks in advance
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Question by:troubleshooter141
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Craig Beck earned 2000 total points
ID: 40572270
Just use the in direction when applying the ACL to the SVI to see if that helps - don't use the out ACL.
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Expert Comment

by:Feroz Ahmed
ID: 40580311
Hi,

Can you have a look at the Cabling on Swtich end connecting to Specific Hosts .I hope there is Cross Cabling done in between Switch and Hosts that is the reason you are getting Destination Host Unreachable at Firewall end.Or you can just change the switch and look for the Ping Status .
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LVL 47

Expert Comment

by:Craig Beck
ID: 40580318
^^^ ??
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Author Closing Comment

by:troubleshooter141
ID: 40616887
Thanks CraigBeck, removing the access-list from the Out direction fixed the issue.
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