VOIP using Cisco 1721 router & Catalyst 2950 configuration

[fireinthecisco]

Hi guys,
I need a little help, my cisco knowledge isnt too hot so please be gentle.

Basically I need a little help on an upcoming project I am trying to get to speed with at work.

We are going to be integrating some VOIP telephones, split between a main site and a remote site, linked by a 10mbit fibre with a cisco 1721 router and catalyst 2950 switch at both ends.

Am I approaching this the correct way...
-Do I use VLANs, one for the VOIP and one for network data?
-If so, where are they configured? In the 1721 router, 2950 switch? Both?
-How do I give the VOIP quality of service (QOS)?
-Can I specify how much of the bandwidth the VOIP uses?

Thanks for reading and for any help, it is appreciated.

 

[jpm121]

- Yes, you need VLANs. Some people might say add an additional management VLAN, but it's not necessary.

- You'll need to do the VLAns on the router, the 2950 won't. Did you buy voice-enabled IOS for the routers? That will pretty much determine the answers to your next 2 questions.

This isn't something to enter into lightly if your Cisco knowledge is limited. Are you undertaking this alone or is a pro coming to help?

 

[fireinthecisco]

Hi jpm121
It was late last night when I posted and I left out some detail. I'm not alone in this project, the telephone company are supplying the fibre, cisco 1721 routers, ip telephones and configuring a VLAN for VOIP use with the ip telephones.

I am however required to be able to configure a second vlan for data use. I need more insight into how VOIP works with this configuration, so I can double check that the engineers are configuring VOIP properly (with QOS etc) for my own piece of mind.

So I will have in effect two vlans, one for the VOIP, one for data, both configured in the router. Is there no further configuration of the 2950 switch required.. will it in effect behave as a normal switch?

I'm assuming voice-enabled IOS will be in the routers they supply. I will have to check. Assuming so, how is QOS and bandwidth configured for a vlan?

Many thanks for your help

 

[ADB100]

You don't really explain the setup too well?

I assume the fibre will link the 2 2950 switches together and you only have a single 1721, Is this correct?. What version of 2950's are they - i.e. are they running the EMI or SMI features (this is hardware dependant, 'G' models generally run the EMI).

If so you need to create some VLAN Trunk interfaces; 1 between the 2 switches on the Fibre link, and 1 between the 1721 and the 2950 it is connected to. Also create your VLAN's in global config first:

vlan 10
name data
vlan 100
name voice
vlan 900
name native-trunk

interface FastEthernet0/25
description Fibre Interlink
switchport mode trunk
switchport trunk nonnegotiate
switchport trunk native vlan 900
switchport trunk allowed vlan 10,100
!

interface FastEthernet0/1
description To 1721
switchport mode trunk
switchport trunk nonnegotiate
switchport trunk native vlan 900
switchport trunk allowed vlan 10,100
!

!1721 router
!
interface FastEthernet0.10
Description Data VLAN
encapsulation dot1q 10
ip address [data vlan gateway & mask]
!
interface FastEthernet0.100
Description Voice VLAN
encapsulation dot1q 100
ip address [voice vlan gateway & mask]



If you are going to piggy-back PC's off IP Phones then you need to configure each access port to allow the Tagged Voice VLAN, plus the access vlan:

interface FastEthernet0/2
description PC+IP-Phone Port
switchport mode access
switchport access vlan 10
switchport voice vlan 100
mls qos trust [cos, dscp] ! this depends on the QoS design
!

From a QoS perspective you need to know whether you are running the EMI or SMI features on the 2950 - EMI is recommended. You should ideally enable the Expedite Queue and set the weights for the 3 standard queues (this is global on the 2950 and cannot be set per-port):

wrr-queue bandwidth 5 25 70 0
wrr-queue cos-map 1 1
wrr-queue cos-map 2 0
wrr-queue cos-map 3 2 3 4 6 7
wrr-queue cos-map 4 5
mls qos map cos-dscp 0 8 16 24 32 46 48 56

The first command sets the 4 queue weights - Q1 5%, Q2 25%, Q3 70% and Q4 is the expedite queue because it is set to 0. The next 4-lines set what CoS values will map to what queues - Q1 gets CoS 1, Q2 gets CoS 0, Q3 gets CoS 2,3,4,6,7 and Q4 (the expedite queue) gets CoS 5. The 6th line sets the CoS-to-DSCP mappings - CoS 0 to DSCP 0, CoS 1 to DSCP 8, CoS 2 to DSCP 16 etc. Note the last command can only be done on the EMI version.

Ideally your IP Phones should set DSCP 24 for Call Signalling and DSCP 46 for RTP media streams - this is based on Cisco's IP Telephony so may need to be tailored for what you are installing.

The other gotcha is how to inform the IP Phones of the Voice VLAN TAG - with Cisco IP Phones this is done via CDP and is simple with other IP Phones it can be done via DHCP options received when the phone boots initially on the data (untagged) VLAN (Nortel, Mitel) or via a config file that the phone downloads initially (Ericsson).

Lots of companies bypass a lot of this stuff to get things working, and on the face of it you will see everthing working but when you try and add a new phone you spend about 2-hours wondering why it didn't work when you plugged it in..... I would say make sure you get a design from them detailing what they are actually going to configure.

HTH

Andy

 

[fireinthecisco]

Hi Andy,
Thanks for the detailed reply. No there are two cisco 1721 routers which create the link over the 10mbit fibre, this fibre is provided by the telephone company and terminates with ethernet equipment into which a 1721 router is connected at each end and are used to create the link. We are then connecting a catalyst 2950 at each site to create a lan.

The 2950 is a "T" version. I assume the G version has fibre ports? This wouldnt be required as it's already taken care of. All the 2950's I researched come with EI (Enhanced Image) software, EMI or SMI didnt appear to be listed for them?? They havent arrived yet so I cannot check. How much different is your configuration now?

The IP phones have their own separate ethernet socket so no piggybacking required.

Thanks again

 

[ADB100]

OK

You need to create a Network between the 2 sites on the 1721 routers (I assume you have WIC-1ENET modules):

interface ethernet1
description WAN Link
ip address 10.1.1.1 255.255.255.252
!

!Other End
interface ethernet1
description WAN Link
ip address 10.1.1.2 255.255.255.252
!

You will need a routing protocol on the 1721's as well, although you only need to send updates over the WAN link:

router eigrp 10
network 10.1.1.0 0.0.0.3
network (data subnet)
network (voice subnet)
!

You will still need a VLAN trunk between the 2950 and the 1721's - one linking to the Voice VLAN and one to the Data VLAN (as previously). Since you are now routing between sites the VLAN ID's can be the same but you will obviously need different IP networks.

You need to check whether your switches run the EMI or SMI, as I said this is hardware dependant and not all 'T' switches run the EMI features (check the software release notes on CCO). With the SMI you cannot trust DSCP, you can only trust CoS, you cannot create QoS policies neither on the SMI.

HTH

Andy

 

[ADB100]

With the routing protocol you would passify the LAN subinterfaces:

router eigrp 10
passive-interface fastethernet0.10
passive-interface fastethernet0.100

Andy

 

[fireinthecisco]

Hi Andy,
Again thank you for your help on this.

I've had an attempt at putting the configuration you suggest together:

The basic IP ranges and subnets I've used are:

Trunk:
router 1 - 10.1.1.1 255.255.255.252
router 2 - 10.1.2.1 255.255.255.252

Vlan1 (voice)
router 1 - 10.1.1.1 255.255.255.0
router 2 - 10.1.2.1 255.255.255.0

Vlan2 (data)
router 1 - 10.1.1.1 255.255.0.0
router 2 - 10.1.2.1 255.255.0.0


!1721 router1
interface ethernet1
description WAN Link
ip address 10.1.1.1 255.255.255.252
!

!Other end – 1721 router 2
interface ethernet1
description WAN Link
ip address 10.1.2.1 255.255.255.252
!

vlan 10
name data
vlan 100
name voice
vlan 900
name native-trunk

interface FastEthernet0/1
description To 2950
switchport mode trunk
switchport trunk nonnegotiate
switchport trunk native vlan 900
switchport trunk allowed vlan 10,100
!

!1721 router1
!
interface FastEthernet0.10
Description Data VLAN
encapsulation dot1q 10
ip address 10.1.1.1 255.255.0.0
!
interface FastEthernet0.100
Description Voice VLAN
encapsulation dot1q 100
ip address 10.1.1.1 255.255.255.0

!1721 router2
!
interface FastEthernet0.10
Description Data VLAN
encapsulation dot1q 10
ip address 10.1.2.1 255.255.0.0
!
interface FastEthernet0.100
Description Voice VLAN
encapsulation dot1q 100
ip address 10.1.2.1 255.255.255.0

router eigrp 10
network 10.1.0.0 0.0.0.3
!data
network (255.255.0.0)
!voice
network (255.255.255.0)
!

router eigrp 10
passive-interface fastethernet0.10
passive-interface fastethernet0.100



Will this work? With reference to QOS - is that the sole resposibility of the 2950's? Is there anything to add to that configuration for QOS in the routers?

 

[ADB100]

You have all the IP addressing messed up - each subnet must be unique:


End A
Voice VLAN 10.1.2.0/24
Data VLAN 10.1.3.0/24
WAN 10.1.1.1/30

End B
Voice VLAN 10.1.4.0/24
Data VLAN 10.1.5.0/24
WAN 10.1.1.2/30

HTH

Andy

 

[fireinthecisco]

Hi Andy,
I had assumed they were separate because I had used separate subnet masks.. ok it probably over complicated matters..

What about this config now (using the subnets you suggested)?


!1721 router1
interface ethernet1
description WAN Link
ip address 10.1.1.1 255.255.255.252
!

!Other end – 1721 router 2
interface ethernet1
description WAN Link
ip address 10.1.1.2 255.255.255.252
!

! 2950 T
vlan 10
name data
vlan 100
name voice
vlan 900
name native-trunk

interface FastEthernet0/1
description To 2950
switchport mode trunk
switchport trunk nonnegotiate
switchport trunk native vlan 900
switchport trunk allowed vlan 10,100
!

!1721 router1
!
interface FastEthernet0.10
Description Data VLAN
encapsulation dot1q 10
ip address 10.1.3.1 255.255.255.0
!
interface FastEthernet0.100
Description Voice VLAN
encapsulation dot1q 100
ip address 10.1.2.1 255.255.255.0

router eigrp 10
network 10.1.0.0 0.0.0.3
!data
network 10.1.3.0
!voice
network 10.1.2.0
!
router eigrp 10
passive-interface fastethernet0.10
passive-interface fastethernet0.100



!1721 router2
!
interface FastEthernet0.10
Description Data VLAN
encapsulation dot1q 10
ip address 10.1.5.1 255.255.255.0
!
interface FastEthernet0.100
Description Voice VLAN
encapsulation dot1q 100
ip address 10.1.4.1 255.255.255.0

router eigrp 10
network 10.1.0.0 0.0.0.3
!data
network 10.1.5.0
!voice
network 10.1.4.0
!

router eigrp 10
passive-interface fastethernet0.10
passive-interface fastethernet0.100



Will this work ok now?

 

[fireinthecisco]

Heres's a (dodgy) diagram of the new layout...

(siteA) |2950|----|1721A|<-----fibre----->|1721B|----|2950| (siteB)

Site A
Router 10.1.1.1/30
Vlans:
Voice 10.1.2.0/24
Data 10.1.3.0/24

Site B
Router 10.1.1.2/30
Vlans:
Voice 10.1.4.0/24
Data 10.1.5.0/24

 

[ADB100]

That should work. The EIGRP network statements are a bit messy and you need to understand it's behaviour with subnets and summarisation. The following will work if configured on both 1721's:

router eigrp 10
passive-interface fastethernet0.10
passive-interface fastethernet0.100
network 10.0.0.0

Since all networks are subnets of major network 10.0.0.0/8 and you don't have any other networks in the way no automatic summarisation will take place.

You will obviously need to 'no shut' each of the major interfaces on the 1721's......

HTH

Andy

 

[vlf]

If you're having this kind of problem, VoIP is not a good place to not know what your doing. Have you thought of hiring an outside contractor? Getting it set up is not the hard part here...