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Ping Question

Bl8ckr0uter

When you are on a router and you execute the ping command, what is the source ip address that is used for icmp? I know that you can specify the address by using the source command but what does it default to? I am refreshing myself on ACLS and I noticed that ACLS will not filter traffic generated from the router...Does this mean if I create an ACL that blocks pings from the 192.168.1.1 network and apply it to an interface AND then go on my router and ping some network and use the source command to specify the 192.168.1.1 ip address (lets say this is F0/1) would the ping still be successful?

EDIT: This doesn't make sense to me at all. I don't understand how you could apply a ACL to a routing protocol if ACLS don't filter traffic generated from the router. Am I crazy (don't answer that I know that answer)?

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Comments

networker050184

The ping will use the address of the out going interface by default.

ACLs applied to the interface do not affect the traffic generated by the router. You can use ACLs for policies on your router for routing protocols or other traffic policies. There are also things like CoPP to filter traffic destined to the router.

APA

phoeneous wrote: »

Yeah, my initial guess is the exit interface closest to the destination.

Spot on... unless you specify a source IP via the extended ping command.