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yaplej
Premium
join:2001-02-10
White City, OR

MPLS and backup ISDN line

Good evening,

One of our sites had an outage that spanned two workdays, and there was nothing our provider could do until the LEC got the issue resolved.

So now I'm looking into providing a backup to the DS1 at each of our remote locations, but would ISDN work when our network is MPLS? Can it dial directly into an MPLS network somehow?

Thanks.

Euphrates

join:2007-04-30
Bellingham, WA
Well, ISDN is a digital dail-up line from a telco provider for the most part. Basically, from what I understand, you can do ISDN a couple of ways. You can use it as a leased line where it would be like a dedicated point-to-point line from one location to the other. The ISDN device will dail the other ISDN device when the MPLS network goes down to maintain connectivity. Dial-on-demand basically. The other way would be to use it for internet and gain access to the the other location (depending on if your MPLS is your gateway to the internet as well as connecting the locations together). Pricing varies depending on who you go with.

I won't attempt to understand MPLS as I haven't dealt with the technology but I've dealt with customers using the setup I explained above to help them out if a poing-to-point or point-to-multipoint T-1 or Frame goes down.

aryoba
Premium,MVM
join:2002-08-22
kudos:4

2 edits
reply to yaplej
For providing backup connection to remote locations, there are several choices

1. Have another MPLS T1 circuit from another provider
2. Use your existing provider POP (over non-MPLS network)
3. Have a long-haul T1 circuit or long-distance ISDN circuit from existing provider to reach remote locations
4. Have a broadband connection (DSL or Cable) and run VPN over it to reach remote locations

Option 1, 2, and 3 should be the best approach since they are from connection perspective is more stable and reliable. However these options are probably financially prohibitive; especially on ISDN where you have to pay significant amount for the long distance connection.

Option 4 is the most economical choice and you are still able to run constant dynamic routing over both existing T1 and over the VPN. However since the circuit is broadband, the SLA will be lower than your existing T1 circuit.


jester121
Premium
join:2003-08-09
Lake Zurich, IL
I've started deploying Comcast business internet service for some clients as a cheap backup option, for the simple reason than when a backhoe takes out a bundle of telco lines (including redundant T1s, ISDN, fiber, etc) it doesn't matter what connection technology you're using. When possible we keep the coax on a different path from the curb to the building.

Wireless is another option as a backup too, but you want a provider that is as isolated as possible from your main circuits.

Euphrates

join:2007-04-30
Bellingham, WA
reply to yaplej
I would guess then that the key is to see if it's the MPLS part of the network that is taking a dump or something in the core that would affect other services as well. In that case you would want to, as jester121 put it with his wireless solution, someone who's network is independent of the problems associated with the problems your current provider is having or may have in the future.


yaplej
Premium
join:2001-02-10
White City, OR
reply to yaplej
It was not the MPLS network that went down. It was a LEC issue with the equipment the provides the DS1 local circuit. ISDN, and phone services was unaffected in this case.

aryoba
Premium,MVM
join:2002-08-22
kudos:4

2 edits
If the main site that had LEC issue already had ISDN circuit, then usually all other sites need to have ISDN circuit to match. The main site then will dial into the other sites ISDN number to connect.

Technically speaking, other sites don't need to have ISDN circuit for the main site to connect using its ISDN circuit. The main site will then dial the provider ISDN number in order to reach your other main sites. In other words, the provider ISDN number/circuit is used as POP to reach your other sites.

When you are thinking of using the main site ISDN circuit to connect to the provider POP to reach other sites, then this is something that you need to discuss with your provider. I'm not sure if your provider are willing to provide their ISDN number to you as the POP to reach your other sites. Usually connection to provider POP is in form of T1, DS-3, OC-X circuit or similar and not ISDN.


No7

@btcentralplus.com
reply to yaplej
There are a few ways you can do it depending on the type of MPLS access circuit and if its a dynamic or static circuit.
Backup scenarios Ive seen are branch to host site,i.e. the site dials into a the main HQ site or DR site -this central site should be a dynamic MPLS site(run BGP).
Meshed dial is too complex and remember the MPLS core uses BGP which can take 30 seconds plus to converge .Backup will not be instantaneous and there will be caveats.

1.You need a reliable mechanism for triggering the ISDN backup at the branch.This can be a simple static route i.e.
serial MPLS interface
ip route 0.0.0.0 0.0.0.0 S0.1 name MPLS
ip route 0.0.0.0 0.0.0.0 dialer1 240 name ISDN-backup
DSL MPLS interface (if PPPoA)
ip route 0.0.0.0 0.0.0.0 name MPLS
ip route 0.0.0.0 0.0.0.0 dialer1 240 name ISDN-backup
These are simple but wont protect against MPLS VPN failure.

Its more reliable to run BGP to the PE router or IBGP tunnelled from the host /DR site -anything to give you a dynamic learned default route that can fail.With some DSL circuits you will have to use IBGP if you want dynamic backup.

2. You either need to advertise the branch LAN subnet via RIP over ISDN to the Host site or have seperate floating static routes at the host end.

3.You need to advertise a suitable summarised route out into the MPLS cloud from the Host site which will be a return route i.e .This will allow the site under ISDN backout to breakout from the host and to connect to other sites in the VPN .You need to be carefull , its easy enough if the sites have contigous LAN addressing but you may end up hijacking traffic to non MPLS sites.

hope this helps