SRST- DHCP best practices

Unanswered Question
Dec 4th, 2007

I`m installing a SRST site with the DHCP for P.C`s across the WAN with a renew time of several days e.g 5 days, normally is best to have a local DHCP for voice only on the SRST router ? It has also been suggested that I do not do this local DHCP set up but rely on the remote DHCP and the re-new time being good enough since the WAN outage should be repaired before the x day limit, also you only have to managed one DHCP. If I go with the remote DHCP and the outage goes beyond 5 days what will happen to the phones, does not having a voice only DHCP in the SRST effect anything else- thanks

I have this problem too.
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allan.thomas Tue, 12/04/2007 - 02:24

Firstly if you provision DHCP on the local voice-gateway then you can save the bindings to a file on the flash, this ensures that if the router reloads then devices can retain the existing IP addresses.

Typically an IP Phone/PC will retain it's existing IP address if it is unable to query the DHCP server, this may not be the case for Thin-Clients however.

With Hub and spoke deployments, it is certainly possible to configure both a voice and data vlan and dhcp scopes for the local LAN by configuring a trunk interface on the voice gateway and LAN switch.

Depending on the size of the remote office you may feel that a centralised DHCP server is the safest option.

However for a small branch office I would recommend configuring DHCP on the local gateway, one scope for the voice VLAN with the CallManger TFTP option, and the other for Data. In this scenario DHCP will be provisioned at all times.




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