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Beginner

arp command

Example: arp 192.168.100.1 0000.000c.2345 arpa

Why when using the above command must you specify the encapsulation type if that is already defined at the interface?

4 REPLIES 4
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VIP Mentor

Re: arp command

Hello,

AFAIK, you do need to specify the encapsulation type, because the command is global and the mapping not tied to a specific interface. I think the command is not even accepted with the encapsulation type at the end (at least not for the platforms I have tried, 1600, 2500).

HTH,

GP

Highlighted
Beginner

Re: arp command

I did it on a 3640 and the encapsulation type is required as an arguemnt (it's not an option to leave it out).

However, your statement "the command is global and the mapping not tied to a specific interface" was my point.

For example let's say you typed the following command "arp 192.168.100.1 0000.000c.2345 arpa" then there would be an entry in the arp cache that mapped that IP address to that MAC address.

Now let's say that traffic entered the router that was destined for 192.168.100.1 but the 192.168.100.0/24 network was out the token ring 0 interface.

Will the router encapsulate the traffic as token ring or arpa when it forwards it our tr0? If it encapsulates it as token ring then it seems that the arpa argument at the end of the arp command is kinda pointless.

Highlighted
Beginner

Re: arp command

I did it on a 3640 and the encapsulation type is required as an arguemnt (it's not an option to leave it out).

However, your statement "the command is global and the mapping not tied to a specific interface" was my point.

For example let's say you typed the following command "arp 192.168.100.1 0000.000c.2345 arpa" then there would be an entry in the arp cache that mapped that IP address to that MAC address.

Now let's say that traffic entered the router that was destined for 192.168.100.1 but the 192.168.100.0/24 network was out the token ring 0 interface.

Will the router encapsulate the traffic as token ring or arpa when it forwards it our tr0? If it encapsulates it as token ring then it seems that the arpa argument at the end of the arp command is kinda pointless.

Highlighted
VIP Mentor

Re: arp command

Hello,

good question...I am not sure what happens, if the static entry overrides the interface encapsulation or vice versa. Can you test this ? I do not have access to a Token Ring device....

Regards,

GP

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