[cisco-voip] WAN site config

[Nick Griffin]

It depends on if you would like to centrally manage dhcp services or
not. A few small remote sites, it's probably practical to provide for
dhcp from the local router or switch. This also provides for
survivability in the event of a WAN failure in regards to dhcp. As for
who(what vlan) gets addresses from the DHCP server is determined by the
vlan interface and the networks defined within the dhcp server. Ie, if
my dhcp broadcast is received from say vlan interface 100(network
192.168.100.0/24) and there is no 192.168.100.0/24 pool defined in the
server, an offer will not be sent. Furthermore, if dhcp is not directly
connected on say a local router and no helper address is configured, the
requested will not be forwarded anyway. 

 

A small router with a switch module terminating phones could be
configured like the example below:

 

ip dhcp pool Phones

   network 192.168.111.0 255.255.255.0

   default-router 192.168.111.1

   domain-name blah.com

   option 150 ip 192.168.4.8

!

ip dhcp pool Data

   network 192.168.11.0 255.255.255.0

   default-router 192.168.11.1

   option 150 ip 192.168.4.8

   domain-name blah.com  

!

interface FastEthernet1/0

 description phone port

 switchport trunk native vlan 11

 switchport mode trunk

 switchport voice vlan 111

 mls qos trust cos

!

interface Vlan11

 description Data Vlan Interface

 ip address 192.168.11.1 255.255.255.0

!

interface Vlan111

 description Vlan Interface

 ip address 192.168.111.1 255.255.255.0

 

 

If say a layer 3 switch was in the mix with vlan interfaces defined for
the local host/phones default gateway, a ip helper would need to be
configured to point to the upstream dhcp server, where your required
dhcp pools would be configured.

 

Hope that helps,

 

Nick Griffin

 

 

________________________________

From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Ortiz, Carlos
Sent: Wednesday, September 14, 2005 8:54 AM
To: cisco-voip at puck.nether.net
Subject: [cisco-voip] WAN site config

 

Is it best practice to configure a remote wan (frame) site for local
DHCP from the router for the phones?  How do you control which VLANS
receive the DHCP addresses?

 

Carlos 

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