ACL: Reflective versus established
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Posted by JF Mezei on January 24, 2010, 4:10 am
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I've managed to get reflective ACL working. However, it adds ACL rules at the end of the ACL. Lots of rules when the LAN side machine makes a lot of connections to the outside world. It creates a lot of redundant entries at the bottom such as : permit tcp host 190.10.0.111 eq 52140 host 64.235.219.134 eq 6881 even though the acl already contains a : permit tcp any any eq 6881 From a performance point of you, is it better to use the "established" mechanism for tcp and use reflective only for udp ? This would greatly reduce the number of dynamic entries in the ACL. for instance: ip access-list extended ACLinbound evaluate Reflect_outbound permit tcp any any established permit tcp any 10.0.0.0 0.0.255.255 eq www deny tcp any any eq 445 ip access-list extended ACLoutbound permit tcp any any permit udp any any reflect Reflect_outbound For tcp, does the reflective mechanism provide any additional functionality that the "established" mechanism doesn't ? | ||||||||||
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Posted by Rob on January 24, 2010, 7:45 am
Please log in for more thread options  it looks much more tidy. Some purists will argue that "established" is a leak because it permits traffic like RST or SYN ACK packets to a nonexisting connection, but I don't see it as a real problem. | ||||||||||
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> at the end of the ACL. Lots of rules when the LAN side machine makes a
> lot of connections to the outside world.
> It creates a lot of redundant entries at the bottom such as :
> permit tcp host 190.10.0.111 eq 52140 host 64.235.219.134 eq 6881
> even though the acl already contains a :
> permit tcp any any eq 6881
> From a performance point of you, is it better to use the "established"
> mechanism for tcp and use reflective only for udp ? This would greatly
> reduce the number of dynamic entries in the ACL.