Interface question 2

[DanielUK]

Hi,

Can someone explain in simple terms how the different interfaces relate to each other on my 801 Router? I'm pretty confused, especially when it comes to applying an access list to an interface e.g. are ACLs always on Ethernet0? In my config I have reference to BRI0, Ethernet0 and Dialer1.

Thanks

Dan

 

[vipergg]

No you can apply ACL's to any active interface on the router . They will function the same whatever interface you apply them to . BRI and dialer interfaces refer to a ISDN connection and of course an E0 is a 10 meg ethernet interface . You create a ACL at the global level and then apply it on a interface either inbound or outbound .

 

[DanielUK]

Thanks Vipergg,

Are you saying there's no preference to a particular interface when applying an access list either outbound or inbound? I've been applying my ACLs to Ethernet0 but wondering if in fact it should be BRI0....

Also, what is the difference between BRI0 and Dialer1?

Dan

 

[chieftan999]

Defined within Cisco documentation:-

If outbound always apply the access list to the closest interface to exiting the network and if inbound then the closest interface to the receiving end.

The reason is, if you deny from the first interface packets destined for an address that they are not allowed to go to but are allowed in other areas outside the interface, then there will be problems.

 

[DanielUK]

Thanks Chieftan999,

So, on my 801, nearest outbound would be BRI0 and nearest inbound would be Ethernet0. Where does Dialler1 fit in? I'm presuming it sits between Ethernet0 and BRI0.

Thanks

Dan