Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Computing > Cisco > Multilink with two T1s -- need sample config

Reply
Thread Tools

Multilink with two T1s -- need sample config

 
 
Bob Wilson
Guest
Posts: n/a
 
      07-16-2004
I haven't been out to this site yet. They say they have a Cisco 2560
(another time they said 2561) with a T1, and are adding a second T1
and want me to do the router part and multilink them.

I can't find any info on 2560 series and don't think I've seen one,
don't even know if they have T1 cards or CSU/DSU via the serial ports.
I haven't talked to their technical person yet, so all that will get
straightened out. Since one T1 is working right now, I"ll be able to
set the second one up to match it.

What I am unsure about is -- once I've got the two T1s firing okay and
-- I think -- I configure ppp multilink on the interfaces, I don't
know where or how to set the IP address they'll use, or maybe to use
ip-unnumbered.

I did RTFM, but the multilinking is discussed a lot more under BRI
setups and didn't look like it would quite fit the same with PRI and I
don't know how different PRI is going to be.

Thanks in advance if someone can post me a piece of a working config
with two T1s multilinked.

Bob W.
 
Reply With Quote
 
 
 
 
Prince By-Tor
Guest
Posts: n/a
 
      07-16-2004
On 15 Jul 2004 21:19:04 -0700, http://www.velocityreviews.com/forums/(E-Mail Removed) (Bob Wilson) wrote:

>I haven't been out to this site yet. They say they have a Cisco 2560
>(another time they said 2561) with a T1, and are adding a second T1
>and want me to do the router part and multilink them.


Could be a 2650 or 2651. I'm not familiar with a 2560 (though that
doesn't mean it doesn't exist.

>I can't find any info on 2560 series and don't think I've seen one,
>don't even know if they have T1 cards or CSU/DSU via the serial ports.
> I haven't talked to their technical person yet, so all that will get
>straightened out. Since one T1 is working right now, I"ll be able to
>set the second one up to match it.
>
>What I am unsure about is -- once I've got the two T1s firing okay and
>-- I think -- I configure ppp multilink on the interfaces, I don't
>know where or how to set the IP address they'll use, or maybe to use
>ip-unnumbered.


Well, what's on the other end? That will affect things...but in
theory you should be able to bond them with ppp multilink. I've never
bonded T1s though.

>I did RTFM, but the multilinking is discussed a lot more under BRI
>setups and didn't look like it would quite fit the same with PRI and I
>don't know how different PRI is going to be.


Are they PRIs or just standard T1s?

--me
 
Reply With Quote
 
 
 
 
Bob Wilson
Guest
Posts: n/a
 
      07-16-2004
Prince,

Thank you for responding -- I talked again to the non-technical person
just now and learned that the router is a 2621. Makes me a lot more
comfortable, as two T1s on a 2500 sounds like too much of a load. I
still haven't gotten the number of the engineer so I don't know how it
interfaces with the T1s -- if it's a 2600 series it could either have
CSU/DSU module(s) or serial ones. And I THINK it connects to a single
router at the provider end.

I did search some more on past threads and now question whether these
T1s even need to be multilinked, or if I just put the ideal parameters
and same metric on both interfaces and let Cisco load-balance. Any
thoughts? In either case I don't know how to assign the IP
address(es). That's why it would help a lot to see a working ru.

These guys are so non-technical that they want to set it up during
business hours. I told them they would have Solitaire and that's
about it. Battleship is out.

Thanks again,

Bob
 
Reply With Quote
 
Prince By-Tor
Guest
Posts: n/a
 
      07-17-2004
On 16 Jul 2004 14:35:15 -0700, (E-Mail Removed) (Bob Wilson) wrote:

>Prince,
>
>Thank you for responding -- I talked again to the non-technical person
>just now and learned that the router is a 2621. Makes me a lot more
>comfortable, as two T1s on a 2500 sounds like too much of a load.


Me too...a 2621 should handle that no problem.

>I
>still haven't gotten the number of the engineer so I don't know how it
>interfaces with the T1s -- if it's a 2600 series it could either have
>CSU/DSU module(s) or serial ones. And I THINK it connects to a single
>router at the provider end.
>
>I did search some more on past threads and now question whether these
>T1s even need to be multilinked, or if I just put the ideal parameters
>and same metric on both interfaces and let Cisco load-balance. Any
>thoughts? In either case I don't know how to assign the IP
>address(es). That's why it would help a lot to see a working ru.


OK.

If it's a single router at the other end, best to just weight both
interfaces the same. Presumably you're using a routing protocol like
BGP or something that will do load balancing...if BGP, be sure to add
"maximum-paths 2" to your router bgp section.

For IPs, just use a pair of /30 subnets...I would think the provider
would give those but you never know. Assuming serial interfaces,
then, you'd have something like:

interface s0/0
ip address 192.168.1.2 255.255.255.252

interface s0/1
ip address 192.168.1.6 255.255.255.252

And the provider would have .1 and .5, respectively. Then, let's
pretend you're using BGP, and your internal AS is 64000 and the
provider's is 64500:

router bgp 64000
neighbor 192.168.1.1 remote-as 64500
neighbor 192.168.1.1 soft-reconfiguration inbound
neighbor 192.168.1.5 remote-as 64500
neighbor 192.168.1.5 soft-reconfiguration inbound
no auto-summary
maximum-paths 2

I'm oversimplifying...you probably want route-maps or prefix-lists
blocking certain routes both ways but without knowing the exact
topology I can't tell you for sure.

Alternatively, you can just static it:

ip route 0.0.0.0 0.0.0.0 s0/0
ip route 0.0.0.0 0.0.0.0 s0/1

(By pointing the routes at an interface, if one of the circuits goes
down that particular static will drop out of the routing table so you
don't lose 50% of your packets.)

Again, replace the default with whatever specifics you might need if
this is not an Internet connection.

Let me know if you have further questions.

>These guys are so non-technical that they want to set it up during
>business hours. I told them they would have Solitaire and that's
>about it. Battleship is out.


That's not always so bad...the worst are the ones who THINK they are
technical, insist that things be done a certain way, and then ask you
to put a static route in...when you ask, "What's the next hop?" they
say, "Next hop? What's that?"

--me


 
Reply With Quote
 
AnyBody43
Guest
Posts: n/a
 
      07-18-2004
Prince By-Tor <(E-Mail Removed)> wrote
> On 16 Jul 2004 14:35:15 -0700, (E-Mail Removed) (Bob Wilson) wrote:


> > And I THINK it connects to a single
> >router at the provider end.
> >
> >I did search some more on past threads and now question whether these
> >T1s even need to be multilinked, or if I just put the ideal parameters
> >and same metric on both interfaces and let Cisco load-balance. Any
> >thoughts? In either case I don't know how to assign the IP
> >address(es). That's why it would help a lot to see a working ru.


> If it's a single router at the other end, best to just weight both
> interfaces the same. Presumably you're using a routing protocol like
> BGP or something that will do load balancing...if BGP, be sure to add
> "maximum-paths 2" to your router bgp section.


MPPP and packet level load sharing have different behaviours.

MPPP is VERY like a single higher speed link. The others are not.
MPPP will have a lower 'hop latency' and does perfect load sharing.
'Hop latency' is my term. It is the time taken to transmit
all of the bits comprising the packet under consideration
on to the wire. (Someone may know of a generally accepted term,
Vincent?) It excludes the time taken for a bit to transit the wire.
e.g. for a 1Mbps line and a 1,000 bit packet the hop latency
will be 1ms.

MPPP will use more CPU than CEF per packet or any of the
'fast switching' per flow methods, however a 2621 would
I guess be OK with 2 x T1 and MPPP.

IIRC MPPP can be configured to bring down a link in the event that
the error rate is over some threshold (or maybe I just made it up?).

A search of CCO on [multilink ppp serial], 2nd hit is
"Multilink PPP on Back-to-Back Routers with Multiple Serial Interfaces"
I would guess that the configuration details there might help

I suggest that you follow whatever recommendations your provider
makes since you will most likely depend on them for support and
there is no point in insisting on them doing something out
of the ordinary unless you have very good reason.
 
Reply With Quote
 
M.C. van den Bovenkamp
Guest
Posts: n/a
 
      07-18-2004
AnyBody43 wrote:

> 'Hop latency' is my term. It is the time taken to transmit
> all of the bits comprising the packet under consideration
> on to the wire. (Someone may know of a generally accepted term,
> Vincent?)


That's 'transmission delay', IIRC.

Regards,

Marco.

 
Reply With Quote
 
Bob Wilson
Guest
Posts: n/a
 
      07-19-2004
Marco, Prince,

Thank you guys very much for the insights, info and references. I'll
put all this together and look at that piece in CCO, and I think I"ll
have a critical mass to do a good job with the situation I encounter
when I go over there Tuesday nite.

Best to all,

Bob W.
 
Reply With Quote
 
Bob Wilson
Guest
Posts: n/a
 
      07-21-2004
A last message to say thanks one more time -- I showed up at the
facility today with way too many people watching over my shoulder.
Company #1 hired me to do the job for Company #2 which was taking care
of the client Company #3, God knows what they were charging for my
time with all those markups... and long story short, I used the
knowledge I've gained from you guys and especially AnyBody43 this past
two days and bonded the two T1s and it worked without a hitch. When I
rode away, they asked "Who WAS that masked man?"
 
Reply With Quote
 
smoove
Guest
Posts: n/a
 
      08-03-2004
Here is the easy way

create a multilink interface

interface Multilink2
description XXXXXXXX
ip address XXXXXXXX 255.255.255.252
ppp multilink
no ppp multilink fragmentation
multilink-group 2



And then setup the interfaces


interface Serial2/0
no ip address
encapsulation ppp
service-module t1 timeslots 1-24
service-module t1 remote-alarm-enable
service-module t1 fdl ansi
ppp multilink
multilink-group 2
!
interface Serial2/1
no ip address
encapsulation ppp
service-module t1 timeslots 1-24
service-module t1 remote-alarm-enable
service-module t1 fdl ansi
ppp multilink
multilink-group 2




"Bob Wilson" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
>I haven't been out to this site yet. They say they have a Cisco 2560
> (another time they said 2561) with a T1, and are adding a second T1
> and want me to do the router part and multilink them.
>
> I can't find any info on 2560 series and don't think I've seen one,
> don't even know if they have T1 cards or CSU/DSU via the serial ports.
> I haven't talked to their technical person yet, so all that will get
> straightened out. Since one T1 is working right now, I"ll be able to
> set the second one up to match it.
>
> What I am unsure about is -- once I've got the two T1s firing okay and
> -- I think -- I configure ppp multilink on the interfaces, I don't
> know where or how to set the IP address they'll use, or maybe to use
> ip-unnumbered.
>
> I did RTFM, but the multilinking is discussed a lot more under BRI
> setups and didn't look like it would quite fit the same with PRI and I
> don't know how different PRI is going to be.
>
> Thanks in advance if someone can post me a piece of a working config
> with two T1s multilinked.
>
> Bob W.




 
Reply With Quote
 
 
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bonding two T1s jhud@osceola.org Cisco 15 05-09-2011 10:05 PM
HELP! Multilink PPP w/3 T1s and a seperate 4th T1 rajuliano@gmail.com Cisco 6 08-30-2006 02:46 AM
Two independent T1s on a 2610? Chris Cisco 3 06-13-2006 11:53 PM
multilink ppp only works with ppp multilink fragment disable (2 T-1s) Karnov Cisco 1 05-24-2004 02:37 AM
two T1s al Cisco 2 10-25-2003 04:14 AM



Advertisments