Category Archives: VLAN

The New Voice LAN

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 – 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
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
calling-info pstn-to-sip from name set beigebox
calling-info pstn-to-sip from number set 70001
sip-server ipv4:<PBX IP>:5060

Asterisk sip.conf config snippet:

host=<2621 Management IP>

Home layout: Layer 2

I’m just finishing up a CCNA preparatory class at the local community college (I had no idea what to expect on the exam, so thankfully I stumbled across this class). I’d definitely recommend the course – the instructor (Shawn Cannady) has done an excellent job covering a wide volume of material in a rapid pace.

One of my classmates recently asked about how I was segmenting off the public wireless from my home LAN. As VLANs, VTPs and PPP were subjects covered in the course, I wrote the following article for the class Wiki:

In the United States, many (but not all) providers use PPPoE to establish the layer 2 connection over ADSL. The upside to this method is increased accountability/manageability, as well as the ability to resell the connection to 3rd parties (For non-resold lines, Telcos are shifting to DHCP-only connections however, as there’s less overhead involved)

Background: Many smaller ISPs use the local Telco DSLAM equipment along with dedicated circuitry and L2TP tunnels back to the smaller ISP routers – which terminate the PPP sessions. In such an instance, connections are routed to individual ISPs based on the realm in the authenticating username []. The smaller ISP can then use their ARIN assigned network to assign globally routed IP addresses.

Working for such an ISP, I often take advantage of this setup – creating new PPPoE username and passwords on our system for individualized connections. Instead of having 3 separate ADSL lines for 3 different Internet connections, I use 1 single ADSL line for 3 different Internet connections. Each “unique” connection has it’s own PPPoE username/password and IP. (The only downside: Each connection shares the bandwidth of the 1 line).

The upside to this configuration is the isolation of Layer 3 – not all connections pass through the same router on my end of the connection. They do, however, pass through the same switch(es) and ADSL modem (however, at layer 2). Instead of worrying about access-lists to prevent different subnets from communicating with each other, I simply worry about inbound traffic from the WAN side on each connection.

My current home layout (simplified here) contains 2 switches. Switch A is located in my office, while Switch B is located where the phone line enters the upstairs. VLAN 2 connects devices directly to the ADSL modem. VLAN1 connects my home LAN to the LAN ethernet of my main home router.

In the above layout, any device connecting to the DSL Link (members of VLAN2), must maintain it’s own PPPoE link to be able to access the Internet. (To simplify this image – imagine that the Wifi router is plugged directly into the DSL modem and configured to connect using PPPoE. Then, imagine the same thing for all members of VLAN 2)

An 802.1q trunk allows the server in my office direct connection to the ADSL modem, and allows my office LAN to connect to the main router (which in turn, routes traffic out the WAN interface PPPoE connection). There are numerous other devices on the LAN.

But why do this???

When I initially decided to provide free wireless access to my neighborhood, I had a few requirements. First of all, I did not want my neighbors connecting to my home LAN. Second, for liability reasons I wanted to the free WIFI to have it’s own globally routed IP address (not an RFC-1918 address NATed with my home static IP). A third requirement was the use of Netflow version 9 to collect various headers from each packet and frame (but not the data payload itself) in the event someone attempted something malicious or a user had major virus issues.

In addition to the WIFI access, on occassion I run dedicated honeypots and malware collectors – obviously servers you want completely isolated from your home LAN.

The above layout is by no means entirely bulletproof, but the added complexity means I don’t have to look over my shoulder as much — and I don’t have to maintain access-lists just for the LAN to live in “separated harmony”