DHCP for ip telephone 2

[charliemao]

hi everyone,

I will develop the AVVID network, one problem is to dispatch ip address to ip telephone, I want to set dhcp server on 4506(core switch), since it is a hotel ,there are 300 IP telephones and 400 analogy phones attached to VG248(analogy gateway), total 700 ip endpoints, is that right? my problem is whether I should use vlans to divide the ip phones in small subnet or make a big subnet just build a dhcp pool as 172.16.91.0 255.255.252.0 which supports 1k hosts? pls give some advice.tks

 

[ADB100]

How many access switches and how are these connected? You have followed a Core, Distribution & Access Model (or collapsed Core/Distribution & Access)?
Your decision as to whether you should have a single VLAN or multiple VLANs should not be based purely on the number of hosts, you need to take into account the physical topology. I always take the stance 'one switch, one VLAN' - i.e. if I have a single 24-port access switch that is connected back to a distribution layer then I would have a unique Subnet/VLAN for that access switch (two Subnet/VLANs if deploying Voice & Data VLANs). You shouldn't span VLANs between access switches (there are exceptions I know so don't preach to me about VMWARE & Clustering...).

Andy

 

[charliemao]

thanks for response. if I set up many vlans(vlan per switch), then I should set up 12 vlans (12 access switch), then how to deal with DHCP issue. the DHCP server is built on core switch 4506, should I set up 12 dhcp pools on 4506?

 

[ADB100]

Yes, one DHCP pool per VLAN/Subnet.

 

[ADB100]

Each VG248 only requires a single IP address - so based on your figures you will have 309 IP endpoints (9 * VG248?) NOT 700.

Andy

 

[charliemao]

thanks again, Each vg248 has a IP address for management, but 48 analog phone FXS will be register on callmanager as an IP device, is it right? so the end points of each vg248 can be regard as 48 IP points. thanks

 

[charliemao]

if I set up 12 dhcp pools on cisco4506, does it work fine? thanks

 

[whykap]

As ADB100 mentioned only one IP address for each VG. The ports do not use and address as they are analog ports.

 

[charliemao]

anyone who sets up more than 10 dhcp pools on core switch(such as cisco4506) ? is that efficient? any problems? thanks

 

[jeter]

Keep it simple! Provide a voic and data vlan and you will be okay.. We just completed a Hotel with around the same number of analog phones and 25 to 30 VoIP phones, and all is good....


SPC NVARNG
Tek-TIP Member 19,650

 

[ADB100]

Keep it simple! Provide a voic and data vlan and you will be okay.. We just completed a Hotel with around the same number of analog phones and 25 to 30 VoIP phones, and all is good....

All well and good but how big is your fault domain with just two VLAN's spanned around 12 access switches? Yeah, the whole network.... One broadcast storm and the whole network is down. Use a separate Voice & Data VLAN per switch and only allow the specific VLANs on each trunk. Set the DHCP scopes on the 'Core' 4500, better still use a real server.

Andy

 

[pndscm]

My opinion would be one VLAN per closet for data and one per voice. I would never do 1 per switch but again, it's my opionion and either method would work. VLAN'ing per switch sounds like too much administrative maintenance for only around 700 endpoints. I just recently visited a college with over 1000 endpoints and they used one VLAN for each data and voice per building. I've seen others all on one VLAN per voice and data.
Here is a sample config of a DHCP scope.

ip dhcp excluded-address 10.1.1.1 10.1.50
!
ip dhcp pool phone
network 10.1.1.0 255.255.255.0
default-router 10.1.1.1
option 150 ip 10.1.1.11

10.1.1.11 is the TFTP server for the IP phones.

 

[charliemao]

ok and thanks