Ip phone forwarding logic for ip packet

[sarahr202]

hi everybody

Let say we have a host Pc want to sends a packet. The host check the destination ip and see if it is on local subnet if it is on the local subnet, host simply forwards it,  if it is not on the local subnet, host simply forwards it to its default gateway.

how does a cisco ip phone behave when forwarding ip packets? For example If ip phone has to contact tftp to download its config or contact the call manager etc.

thanks

[Chris Deren · Accepted solution]

No different, IP phones use IP protocol so the underlying packet traffic looks the same, IP phone just like a PC can send and receive TCP and/or UDP packets and behave appropriately.

HTH,

Chris

[sarahr202]

Thanks for your reply.

Let say our ip phone just powers up and get following from dhcp.

ip 199.199.199.1/24

tftp server    188.188.188.1

default gateway 199.199.199.10

As a part of boot up process, Ip phone has to contact tftp at 188.188.188.1 to download its configuration file.

How will ip phone contact tftp server? will it not create ip packet and sent to default gate way?

thanks

[Chris Deren · Accepted solution]

Here is a doc describing IP phone bootup process:

https://supportforums.cisco.com/docs/DOC-25231

HTH, please rate all useful posts!

Chris

[sarahr202]

Thanks Chris for the nice video.