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New VOIP system - VLAN Routing questions

cyoungblut
Level 1
Level 1

Hello - I have a flat network (one subnet) that we are adding a VOIP system into. We are installing a 4510 Switch in the core and each of the 4 wiring closets will have one 3560-POE 48 port switch with fiber back to the core. I think I understand the use of a separate VLAN for the voice network but I'm having a hard time getting the setup of the separate subnet for the voice vlan and getting that subnet to talk to the other VLAN for configuration from the TFTP server (primary call manager). The 4510 has a primary and secondary supervisor engine. The Primary and secondary call managers are on the data subnet. Can someone point me in the right direction for getting the VLANs and Routing information correct? The ports on the switches will need to run multiple vlans since the computers on the network will hook into the new phones. The new IP phones are mostly 7941s with a few 7911s and 7970s.

Thanks

1 Accepted Solution

Accepted Solutions

You have to have Gateway in your dhcp conf to get it worked.

DHCP Server: 10.0.0.176

Subnet IP Address: 10.0.23.0

Gateway (Option 3) 10.0.23.1

Primary Start IP Address: 10.0.23.10

Primary End IP Address: 10.0.23.15

Subnet Mask 255.255.255.0

Primary TFTP Server (Option 150) 10.0.0.176

Arp Timout 300

IP Addr Lease Time 36000

Renewal (T1) 36000

Rebinding (T2) 36000

cheers,

Masood Ahmad Shah

BLOG: http://www.weblogs.com.pk/jahil/

View solution in original post

31 Replies 31

Amit Singh
Cisco Employee
Cisco Employee

Chris,

I am listing the steps that you need to do :

1. Create two separate vlan on the core switch 4510 and on all the 3560's. You can do it manually or use VTP for propogating vlans from the core to access switches.

2. Create trunk between core and all the 3560 switches.

3. Once the trunking is done, configure the 3560 switch ports to use both the Data and Voice vlan. Do this:

conf t

interface gig 0/1

switchport mode access

switchport access vlan 1 <-- Data Vlan

switchport voice vlan 2 <-- Voice vlan

4. Once the port config is done, configure SVI's on coare 4510 for both voice and data vlan

conf t

int vlan 1

ip address a.a.a.1. b.b.b.0

no shut

int vlan 2

ip address x.x.x.1 y.y.y.0

no shut

You might have to use " ip-helper address " command under the SVI interface if your DHCP server for ip phones is on a diff subnet.

HTH,

-amit singh

ankbhasi
Cisco Employee
Cisco Employee

Hi Friend,

First you need to create 2 vlans in your database. One you alreday have and second you can create.

Once 2 vlans are created you can verify the same using "sh vlan". After that configure your interfaces on which you will connect you ip phone as

switchport mode access

switchport access vlan

switchport voice vlan

Once you are done with this on your sup engine configure inter vlan routing

ip routing

interface vlan

ip address x.x.x.x x.x.x.x

interface vlan

ip address x.x.x.x x.x.x.x

Make sure the ip addresses which you configure on your vlan interfaces should be assigned as the gateway to respective devices in their vlan. Also make sure you configure trunk links between your 3560 switches and 4510 switch allowing only these 2 vlans.

HTH

Ankur

Ok, I have the two vlans created on my core 4510 switch. For now I am just working with that switch and will worry about the trunks to the IDFs later (if that is ok?).

I have data vlan 10 and voice vlan 23. I have my data subnet, ie. 10.0.0.0/24 and a voice subnet ie 10.0.23.0/24. I have DHCP enabled on my Cisco Call manager (ip. 10.0.0.176) to supply IP addresses (in the subnet 10.0.23.0) to the phones. Computers get their IP address from a DHCP server on subnet 10.0.0.0. I'm confused in which IP addresses to put on the VLAN interfaces? Sorry but I've not had to deal with VLANs and switch routing before so I apologize if this is somewhat elementary.

Thanks for all your help.

Hi Friend,

As you mentioned you want vlan 10 for data in subnet 10.0.0.x/24 and vlan 23 for voice in subnet 10.0.23.x/24 you have to create 2 layer 3 interfaces on your sup engine.

Something like this

interface vlan 10

ip address 10.0.0.x 255.255.255.0

interface vlan 23

ip address 10.0.23.x 255.255.255.0

ip helper-address 10.0.0.176

HTH

Ankur

*Pls rate all helpfull post

Hi,

Interface vlan 10

ip address 10.0.0.1 255.255.255.0

no shut

Interface vlan 23

ip address 10.0.23.1 255.255.255.0

ip helper-address 10.0.0.176

no shut

And make sure that these IPs are the gateway of you computers and IP Phones respectively.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

mohammedmahmoud
Level 11
Level 11

Hi,

In the addition of the spectacular explaination from Amit and Ankur, i'd recommend that you use Auxiliary/Voice VLANs:

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_guide_chapter09186a008077444f.html

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

Thank you much - I am learning I think!

Another questions because I'm having difficulty getting the phone to register with the call manager using dhcp. The primary call manager is in the same subnet/vlan as our data network - how does the phone (which is in a different vlan/subnet) know to use the call manager (tftp server) as its dhcp server instead of the dhcp server that our network pcs use. Again, many thanks! I am learning.

Hi Friend,

When your IP Phones send a DHCP request on vlan 23 it will be a broadcast and will hits vlan 23 layer 3 interface on your sup engine where it will be converted to the unicast ecause of ip helper command.

Now the unicast request will be sent by vlan 23 as a source ip address and will reach the DHCP server where DHCP server will inspect the source ip address from where the request had come and when it matches the DHCP pool subnet which you might have created for voice vlan it will return the ip address form voice vlan subnet.

HTH

Ankur

*Pls rate all helpfull post

Hi,

The inter-VLAN routing that you've configured (interface VLAN10 and Interfac VLAN 23 - and make sure that "ip routing" is configured on the switch) will do the reachability job between the 2 VLANs.

On the Interface VLAN 23, put the IP address of the DHCP server that you want the IP Phones to use using the "ip helper-address" command. Further you can configure the DHCP to give the IP phones the tftp server ip address.

Please don't hesitate for any further questions.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

The DHCP server (in this case the primary call manager) can reside in a different subnet and vlan, correct...hence the ip helper-address command?

Also, how do I know if IP Routing is enabled on the 4510 switch. I type in IP Routing from the config line and it accepts the command but I don't see anything when I do show run.

Yes, you are right.

IP routing is enabled by default on Cat4500 Sup engines.It should list under the " show run ". Please paste the output.

To check if it really is working, Type " show ip route " and you should see all the SVI's that you have configured on the box.

-amit singh

Attached are results from my Show Run and Show IP Route (at the end).

I'm only using voice vlan 23 and the native vlan 1 for now.

Hi Friend,

Yes IP routing is enabled on your switch and your config looks perfect. I believe your IP Phones should receive an ip address now from your DHCP server.

Can you confirm the same?

Regards,

Ankur

If I leave the 7911 phone set for DHCP Enabled it wants to pull an IP address from our 10.0.0.0 subnet. It does show as being in Voice Lan 23. If I disable DHCP on that phone and set the IP Address to 10.0.23.11 (an ip in our voice subnet) I get a message "router not in subnet".

I'm thinking it is in the gateway configuration... I have our CM1 set up with IP 10.0.0.176 and have DHCP server running on that with a DHCP pool in the 10.0.23.0 subnet. Is this ok? I want the phones to get an IP from the 10.0.23.0 subnet. Our 10.0.0.0 subnet gateway is 10.0.0.254.

On VLAN 23 I have the IP helper address set to our TFTP Server (which is our CM1, 10.0.0.176). Am I missing the boat on something here? Our 4510 switch IP address is 10.0.0.175.

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