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Sanity Check - ACL

I have a Cisco 827-4V ADSL router and I want to add an incoming ACL to the ADSL interface that will block attempts to spoof traffic from my network addresses (i.e. so someone outside my network cannot send a packet to a host on my network if the packet claims to be from another host on my network).

My network numbers look kinda like this (the last octet of the Broadcast and also the Netmask are the real numbers):

Netmask: 255.255.255.192
Broadcast: 10.70.41.127

My router occupies 10.70.41.65

Would the correct ACL be --> access-list 123 deny ip 10.70.41.64 0.0.0.63

I want to make sure before I put it in place.

ASKER CERTIFIED SOLUTION

bfarmer

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dgroscost

You should probably block the other private IP subnets (192, 127, 10, etc.) on the outside interface as well.

PsiCop

ASKER

I don't disagree, but that wasn't my Question.

PsiCop

ASKER

bfarmer,

Yes, there will be an "any" at the end of the ACL line - I was checking the syntax of the network specification, wanted to make sure I had correctly translated the network information into Cisco's notation.

Yes, there is a lot more to the ACL, and plenty of specific "permits" to allow the things I need before explicit "deny ip any any log" at the end.

bfarmer

PsiCop - Ok, just wanted to make sure. Your translation is correct.