Monthly Archives: June 2010

Asterisk, Cisco, VLAN, VOIP, What?!

The New Voice LAN

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I’ve been meaning to look at the voice capabilities of the 1750’s I’d purchased while studying for my CCNA

(In previous posts I misspoke and claimed they were 1751’s, they are in -fact 1750’s).  The Cisco 1750’s have a slot for Voice Interface Cards, something I’ve not worked with – and something that influenced my purchase of the routers.

PVDM module goes in the top empty slot, DIMM in the right empty slot

I quickly realized I’d need a Digital Signal Processor (PVDM) card (~$90 on ebay) in addition to the VICs – AND I didn’t have enough memory OR flash to run an appropriate IOS image. The Flash upgrade to 32M was appx $30.00, with memory running about the same. Things started to quickly add up.

Right side is where the replaceable Flash goes

Which made me look at the Cisco 2621 also sitting on my work-bench.  Research quickly revealed I was looking at a much more affordable path.  I got a pretty good deal on an NM-2V with 2 FXO cards (ebay – about $115.00 – with the added bonus that the seller lives in my same city, so I saved on shipping and we met in an Aldi’s parking lot):

The NM-2V supports two VIC cards… the FXO (Foreign eXhange Office ~= PSTN origination/termination) and FXS (Foreign eXchange Service ~= provices dialtone service)  cards generally run about $50.00 on ebay, with the NM-2V averaging around $14-$45. So all in all, I paid at or below the average price for the entire package, and it all arrives at the same time. (There are other types of cards as well, but FXO and FXS are the only types I’m concerned with)

My first task is to get enough memory installed in my 2621 to support an IOS image with VOIP and ADSL capabilities. I’d searched around for some time before finding a site that I really like – www.parts-quick.com. They provide full specs on each router, the  max and min memory capabilities, flash upgrades, etc.. and the prices aren’t bad either.

The Glowing Bones of a Cisco 2621

My overall goal is to have one device that handles everything related to the telephone line: DSL termination/bridging, PSTN gateway, and dialtone server – a device I’m affectionately calling “beigebox0″. This will allow me to replace my Zyxel DSL bridge and Linksys PAP-2T, plus actually hook the PBX  into the PSTN. My current layout (an Asterisk box + Linksys PAP-2T)  has only SIP origination/termination, leaving an unused POTS line coming into my house. The new setup will still utilize the Asterisk PBX for voicemail and dialplan processing (as well as long distance over SIP, and an IAX2 trunk to Telephreak) , but use the Cisco 2621 for local call termination (calls in my native ratecenter).

The New Voice Lan (We don't need no stinkin' Visio)

Routing (and PPPoE) will still be handled by the Quagga router.  The Quagga also has a Courier V.32 Voice modem connected to it for troubleshooting dialup POPs, wardialing the 900 or so phone numbers my company owns (for auditing purposes),  and adding a backup connection in the event the DSL line goes dead (of course if dialtone is gone also, I’m out of luck). The modem _could_ be moved over to the 2621’s AUX port, but as all routing occurs at the Quagga, this layout makes more sense.

The link between the 2621 and the PBX could have been done a number of different ways. In the end, I opted to treat the 2621 as being on the WAN side of things, and I am using its management IP for that SIP endpoint. This gives me the ability to filter traffic between the PBX and the “beigebox” at the router. Directly connecting the 2621 to the PBX would reduce hop-count, however also add another location where firewall rules need to be managed and monitored aggressively.

Calls made from the home phone hit the 2621 via the FXS port, and are SIP-ed over the FastEthernet interface through the router and to the PBX.  If the call is long-distance it heads  BACK out the router to my SIP provider, with local calls heading back to the 2621 for connection to the PSTN. All call routing (local and long distance) is determined at the PBX. (The one exception being 911, which is immediately bridged at beigebox0)

Basic flow of an outbound call

Incoming calls from the PSTN (via the FXO voice-port)  will soon be  sent to the PBX for handling – which will initially sends the call back to beigebox0 to ring the home phone (via the FXS port), and following a number of rings sent to voicemail on the PBX.

So far, the layout has functioned perfectly. Next up – finish inbound handling of calls on the PBX (voicemail, etc)

Cisco 2621 config snippet:

hostname beigebox0

voice rtp send-recv
!
voice service voip
sip
bind all source-interface FastEthernet0/0

voice-port 1/0/0
description POTS line
ring number 10
!
voice-port 1/0/1
!
voice-port 1/1/0
description HomePhone
timeouts call-disconnect 10
!
voice-port 1/1/1
description ModemLine
timeouts call-disconnect 10
!

!
!
dial-peer voice 100 pots
description Dialing 411
destination-pattern ^411$
port 1/0/0
!
dial-peer voice 101 pots
description Dialing 911
destination-pattern ^911$
port 1/0/0
!
dial-peer voice 102 voip
description TelePhreak
destination-pattern ^666$
session protocol sipv2
session target sip-server
session transport udp
dtmf-relay rtp-nte
codec g711ulaw
no vad
!
dial-peer voice 200 pots
description PBXManualCallRouting
destination-pattern ^70001…….$
port 1/0/0
forward-digits 7
!

dial-peer voice 300 voip
description PBXConnector
destination-pattern .T
session protocol sipv2
session target sip-server
session transport udp
dtmf-relay rtp-nte
codec g711ulaw
no vad
!
sip-ua
calling-info pstn-to-sip from name set beigebox
calling-info pstn-to-sip from number set 70001
sip-server ipv4:<PBX IP>:5060
!
!
telephony-service

Asterisk sip.conf config snippet:

[beigebox]
type=friend
host=<2621 Management IP>
nat=no
qualify=no
insecure=invite
canreinvite=no
context=beigebox

BrainDeadTip

Wireless Networking in the Developing World

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Greg Sowell had a great link this week in his blog — such a great link that I’m passing it along here.

This is an impressive piece of work.

The book is freely available for download and covers a wide range of wireless topics – including using Solar Energy for power, OLSR for routing, and low-cost tools (including the WiSpy) that can assist in site surveys.

So far I’ve only had a chance to skim the work, but I’m definitely impressed. Now I have some weekend reading to look forward to.

What?!

NetflowLive!

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The good news is this – we’re now up to 30 subscribers on the neighborhood wifi.

Currently 30 subscribers on the wireless

With an average of 1.75 users online at any given moment:

Users online at any given moment.

I’ve also started working on writing a Netflow analyzer application, based off a similar application I wrote for work.  At the current time, this version  only streams real-time connection endpoints and DNS statistics (last resolved sites, most resolved sites), as well as detects TCP SYN scans. Each flow record is also colorized (similar to what you would see in Wireshark), to further categorize the type of connection.

Instead of calling the gethostbyaddr() function on a destination IP  (which simply pulls a PTR record, and in the world of vhosts is a poor representation of where a user is actually connecting),  subscriber DNS queries are syslogged offsite and parsed.  The Netflow Live application I’m building uses those parsed and stored queries to give a fairly accurate determination of what site is being visited when.

Visited URLs could also be determined and logged  if a transparent Squid proxy was utilized on the Access Points. I have NO intention of doing this, however. I’m only concerned with endpoints and protocols being used. The number one protocol in use on the network:  HTTP (Shocking!)

Netflow Live (streaming recent connections)

For those of you unfamiliar with Netflow, it’s a solution put forth by Cisco for IP traffic profiling. The two main elements are an exporter (usually a router) and a collector (which the exporter sends flow data to). Netflow does not include data  payloads , ONLY a log of the endpoints used in each connection. (Think of it this way: When you make a long distance phone-call, you receive a monthly bill that details your phone number called another phone number at a specific time, for a specific duration. The phone company doesn’t actually have record of the conversation, however).

The data collected does include IP source and destination addresses, Transport layer source and destination ports, byte countes, packet counts, TCP flags, and MAC addresses. (Below is all the fields actually captured)

This is all the data that's actually stored from each connection.

So what does this allow? Utilizing Netflow, I can determine subscribers on the network with certain network signatures for viruses, detect some DoS attacks and SYN scans, and graph the most commonly used protocols on the network.

I can also shape traffic based on determinations made by looking at the data. Is someone experiencing bad Skype calls due to someone streaming video over HTTP? I can use the netflow data to reshape things as needed.

So what’s in the works? Using NetGeo data, I plan on mapping connection endpoints on a US world map, allowing a visual display of where in the world most connections are destined.

Orion Netflow offers the same functionality I'm going for - but at a hefty pricetag.

But next up:  I  need to fix the  bug preventing a software reboot of the access points – hopefully I can get to that this weekend.

Update  6/9/2010:

Jake Wilson pointed out the free NetFlow analyzer Scrutinizer by Plixer. I’ve not had a chance to look it over yet – but check out this video about the product.  I first came across that video a month or two ago… it was like staring at the sun, initially I couldn’t tell if I liked it or not – but I watched it like 20 times that day.  GREAT work guys, catchy AND entertaining.