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Configure ingress & egress ACL's on cisco 2811

Posted on 2009-07-09
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Last Modified: 2012-05-07
Hello, I've configured a cisco 2811 for a 56k frame-relay circuit on a private network. One of the security requirements is to setup ingress & egress ACL for inbound/outbound traffic. Can't say i've attempted this yet. I'll have to do all the configuration changes via telnet since the router is at another location. I'll post the configuration I have below (its pretty basic). Any help would be most appreciated. Thanks!




!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname <!>
!
boot-start-marker
boot-end-marker
!
enable password <!>
!
no aaa new-model
!
!
ip cef
!
!
multilink bundle-name authenticated
!
!
!
archive
 log config
  hidekeys
!
!
!
!
!
interface FastEthernet0/0
 ip address <!> 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface Serial0/0/0
 no ip address
 encapsulation frame-relay IETF
 no fair-queue
!
interface Serial0/0/0.777 point-to-point
 ip address 192.168.<!> 255.255.255.252
 snmp trap link-status
 frame-relay interface-dlci 777
!
no ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 192.168.<!>
!
!
ip http server
!
!
!
control-plane
!
!
line con 0
 password <!>
 login
line aux 0
line vty 0 4
 password <!>
 login
!
scheduler allocate 20000 1000
!
end
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Question by:MikeG299
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by:atlas_shuddered
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Have you got a TFTP server on the customer's side?
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Author Comment

by:MikeG299
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No, I do not. I only need to control inbound/outbound ports from 56kwic to fe/0.
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by:atlas_shuddered
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Okay.  Before you start with the ACL I would secure your vty session with ssh and dump telnet.  (Before you disable telnet, confirm that ssh is working and you can connect successully).  Another thing that I would recommend is, starting any changes on a remote router, be sure to issue the command:

#reload 005

This instructs the router to perform a reload in 5 minutes, this way, if you make a change and lose connectivity to the router, the change will be dropped at reload, allowing access again.  Once you are done with your configs, issue the command:

#reload cancel

if more time is needed, follow the above with #reload 005 again.

Finally, try to do as much as you can in notepad and then upload.  Otherwise, you will have to keep saving your work to flash and resetting the reload command if more time is needed.

After you have set up ssh, open notepad and configure your ACLs (if you have ideas of what exactly you want the ACL to filter, post that and I will try to work up an example.)  Build them from the perspective of:

Traffic coming to the LAN from your FR link should be filtered on serial 0/0/0.777 in
Traffic leaving the LAN destined for another network should be filtered on eth 0/0 in

Doing this limits the traffic that is actually processed for routing to only that traffic which is going to be allowed across the circuit to begin with.

Once your ACLs are built, copy and paste them into the router (don't apply them).
Next, apply the ACL that is limiting traffic to the WAN first and tweak it as needed.
Following this, issue the #reload 005 command and apply the second ACL to the serial 0/0/0.777 link.  

Perform a #show run.  If output is returned, breathe a sigh of relief, save to flash and start your review and tweaking.  If not, go get a coke and become scarce for the next 5 minutes.  Upon return, review the ACL for what is locking your remote access and repeat.
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Author Comment

by:MikeG299
Comment Utility
Hi,
Thanks so much for responding.
I've never setup SSH, could you please post an example or some sort of instruction?

The router is on a private network managed by AT&T. There is no WAN or exposure to the WWW.

ON the ACL: I want to allow only sessions over port 3389 in/out, PING in/out, 502 in/out

Thats a great idea on the reload 005. Look forward to your reply.
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atlas_shuddered earned 500 total points
Comment Utility
To set up ssh:

http://www.cisco.com/en/US/tech/tk583/tk617/technologies_tech_note09186a00800949e2.shtml

For your ACLs:
#config t

#ip access-list extended LAN_TO_WAN

#permit tcp any any eq 3389

#permit tcp any any eq 502

#permit tcp any any eq echo

#permit tcp any any eq echo-reply

#deny ip any any log

#exit

#interface eth 0/0

#ip access-group LAN_TO_WAN in

#exit

#ip access-list extended WAN_TO_LAN

#permit tcp (your IP/mask) (router IP/mask) eq telnet

#permit tcp any any eq 3389

#permit tcp any any eq 502

#permit tcp any any eq echo

#permit tcp any any eq echo-reply

#deny ip any any log

#exit

#interface serial 0/0/0.777

#ip access group WAN_TO_LAN in

#end

#copy run start

#exit

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Author Closing Comment

by:MikeG299
Comment Utility
Got it working. Thanks so much; very appreciated.
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