CCNA Voice Study - Integration Models

PBX- Traditional model, phones all have a unique DN perhaps DIDs. Calls come into a receptionist for direction and users must use an access digit of sorts like 9.

Keyswitch – Model in which all phones have a common lines on all of them. All users can see when a line is in use and intra-office calls are rare.

Hybrid- All phones have common lines in addition to a unique one.

Debuging H323 Dial-Peers

Today has been a long day. I’ve been trying to get 4 analog DID, and 4 analog DOD lines working on a 2811 with one FXO and one FXS DID card. Some very useful debug commands in this process have been.

debug voip dialpeer all
This allows me to see when I place an outbound call what Dial-peer it is actually hitting and all the detail about it.

Debug vpm all
This gives me the debug output from the FXO and FXS cards. In my case it’s telling me I need to get a hold of the phone company. The lines are supposed to be Ground-start however when my FXO goes off hook it never sees the circuit complete and then just drops the call.

CCNA Voice Study - Licensing Requirements

IOS License – Straight forward the license for the version of IOS you will be running on the ISR.

Feature License – Is the number of phones that the CUCME will be able to support. Think of it as attached to the ISR verses the phone.

Phone User License – Is the actually license for use and operating the phone. Think of it as attached to the phone verses the ISR.

Licenses can be added incrementally so you could buy a 24 phone license and later purchase a 48 phone license for a total of 72 usable phones.

CCNA Voice Study - CUCME Platform Limits

Platform	Number of Phones
1861	8
IAD2430	24
2801	24
3250	10
3270	50
2811	35
2821	50
2851	100
3725	144
3745	192
3825	175
3845	250

CCNA Voice Study - Unified Messaging Platforms

Product	Number of Users	Redundancy Support	E-mail Support	Server or Router Based
Unity Express	Up to 250	No	Relay voice-mail to outside e-mail server	Router
Unity Connection	Up to 7,500	No	Relay voice-mail to outside e-mail server	Server
Unity	Up to 7,500 per server. Expandable to 250,000 with multiple servers.	Yes	Integrates directly with MS Exchange, Lotus Notes, or Novell GroupWise	Server

CCNA Voice Study - Call Processing Platforms

Product	Number of Users	Redundancy Support	Server or Router Bassed
UC500	8 to 48	No	Router
CUCME	Up to 250 depending on router	No	Router
CUCMBE	Up to 500	No	Server
CUCM	30,000 per cluster	Yes	Server

CCNA Voice Study - Cisco VoIP Structure

Much like the OSI model Cisco has a standardized reference model to explain the various components that make up a unified communications system. From top down:

Endpoints – IP Phones, Cell Phones, Video Phone, IM Client aka what the user touches.

Applications – Voice Mail, Conference Call Apps, Call Center Apps, 911 Services aka feature rich services.

Call Processing – CUCM, CUCME, UC500 aka what handles call flow.

Infrastructure – ASA Firewall, Voice Router / Gateway, Voice switch aka what all the above layers need to communicate together.

CCNA Voice Study - PoE

Cisco pre-standard PoE verses 802.3af PoE

Cisco pre-standard PoE Process
1. Device connected to switch.

2. Switch sends a Fast Link Pulse (FLP) tone to the device. Only unpowered Cisco pre-standard PoE device will loop the FLP back to the switch.

3. Switch receives pulse back and applies a minimal amount of power (6.3W) to the line.

4. Unpowered device boots and communicates it’s actual power requirements via CDP.

802.3af PoE Process
1. Device connected to switch.

2. Constant small DC current is applied to line.

3. 802.3af device is equipped with a resistor and will return a specific level of resistance on the line.

4. Depending on level of resistance switch knows how much power to send to the device.

802.3af Power Class	Power Allocated	Actual Power Used
Class 0	15.4W	0.44W to 12.95W
Class 1	4.0W	0.44W to 3.84W
Class 2	7.0W	3.84W to 6.49W
Class 3	15.4W	6.49W to 12.95W

Class 0 devices are designed to be cheap to manufacture basically just requesting that power be sent to them. Too many Class 0 devices can exhaust your switch power supply as all Class 0 devices will be allocated the full 15.4W.

CCNA Voice Study - IP Phone Boot Process

1. Phone connected to Ethernet switch port. Receives power either via 802.3af or Cisco-Proprietary POE.
2. Cisco switch delivers voice VLAN information to the phone via CDP.
3. Phone now in voice VLAN initiates DHCP request. Switch relays this to DHCP server via ip-helper command.
4. DHCP server offers phone IP address including DHCP option 150, better known as TFTP server.
5. Phone initiates a connection with the TFTP server provided in option 150 of the DHCP response and downloads its configuration file. Included in the configuration file is a list of call processing agents such as CUCM Subscriber, CME ISRs.
6. The phone attempts to contact and register with the first call processing agent, if this fails it moves onto the next until the list is exhausted.

Re: New Author

Well first off, I would like to thank Tim for the warm welcome. Something about my background, much like many people in this field the skills and knowledge I have obtained, come from dealing with issues every day. I have been working in the IT field since 1996, starting in UNIX support, with some light networking, moving into Microsoft, my need and desire to experiment and see exactly how things work has driven me deep into the inner workings of many Microsoft products, the opportunity to write here is very much a privilege for me.


I hope to write on a wide verity of subjects, from ways to solve complicated issues, to in-depth how-to’s for products that may not have clear documentation. I hope that the articles I write here can help others that may have the same frustrations that I have had, and maybe offer some unconventional solutions to problems using tools in ways they were never intended to be used.

New Author

I’d like to welcome a new author to the blog. A long time friend of mine Dave Cathey, he has a long and far reaching background in Microsoft related technologies. I have witnessed first hand some scary MS scripting on the fly for situation based solutions. I would say without a doubt he puts any Microsoft administration skills I have to shame.

With that I hope you’ll look forward to reading what he has to contribute and to round out the blog providing both network and server side components.

Upgrade Rommon

I guess today is a rommon intensive day; I was curious what the process was to upgrade the rommon on a 2801. It’s pretty straight forward. Please note there is no real gain to upgrading your rommon unless there is a new feature that you need which is in the update.

1. Download rommon file for your platform. Example C2801_RM2.srec.124-13r.T5 is the latest and greatest for the 2801.
2. TFTP this file to Flash.
3. Router#upgrade rom-monitor file flash:C2801_RM2.srec.124-13r.T5
4. This will erase the Field-upgrade rommon memory area with the new file and reboot your router.
5. Confirm new rommon loaded with the show ver command output:

ROM: System Bootstrap, Version 12.4(13r)T5, RELEASE SOFTWARE (fc1)

That’s all there is to it.

Default Passwords

Great site for finding the default passwords on OEM equipment, I wouldn’t call it hacking as much as knowing where to go.

http://artofhacking.com/etc/passwd.htm

TFTP Download from Rommon

I got tired of having to look this up all the time so I’m writing it up. So I had a 2801 I foolishly loaded an IOS image on that it didn’t have enough memory for and I got the dreaded reboot loop of death as it loads and crashes.

Solution is to use the break command to drop into Rommon mode and then load a new IOS image via TFTP either direct into DRAM or flash. Issue the following commands in Rommon mode it should assign the IP information to the first interface so on a 2801 FE0/0.

1. IP_ADDRESS=(IP Address)
2. IP_SUBNET_MASK=(Subnet Mask)
3. DEFAULT_GATEWAY=(Default Gateway IP)
4. TFTP_SERVER=(IP of TFTP Server)
5. TFTP_FILE=(File Name of the IOS image)
6. tftpdnld (or a –r to load right into DRAM)

Once booted you could then copy the image onto flash and of course change your boot parameters to match the new ios name and location.