[c-nsp] Multilink PPP Was -> Re: Balancing T1's with CEF

Thu Jul 30 11:38:04 EDT 2009

Here is what I have on a multi-link with AT&T.

interface Multilink1
 description XXXXX
 ip address XXX.XXX.XXX.XXX 255.255.255.252
 load-interval 30
 no keepalive
 no cdp enable
 ppp multilink
 ppp multilink fragment disable
 ppp multilink group 1

interface Serial1/0:0
 description XXXXXXX
 bandwidth 1536
 no ip address
 encapsulation ppp
 no fair-queue
 no cdp enable
 ppp multilink
 ppp multilink group 1
 max-reserved-bandwidth 100

Security Team wrote:
> Well.....we arent' doing per packet and the destinations are definitely
> different.
>
> The last time this problem occurred I did a clear ip cache and it went away.
> Since it isn't doing it this time I guess I thought I should try something
> else.
>
> Here is what I tried, I tried converting to multilink ppp encaps instead of
> HDLC to see if that would have any effect, and it didn't.
>
> (on both ends):
>
> aaa new-model
> aaa authorization network noauth none
> aaa session-id common
>
> interface Multilink1
>  no ip address
>  load-interval 30
>  no cdp enable
>  ppp authorization noauth
>  ppp multilink
>  ppp multilink group 1
>  no shut
> !
> Interface Serial1/1/0
>  encapsulation ppp
>  ppp authorization noauth
>  shut
>  no shut
> !
> Interface Serial1/1/3
>  encapsulation ppp
>  ppp authorization noauth
>  shut
>  no shut
> !
> Interface Serial1/0/0/12:0
>  encapsulation ppp
>  ppp authorization noauth
>  shut
>  no shut
>
> So with 3 static routes like this:
>
> ip route x.y.z.0 255.255.255.0 serial1/1/0
> ip route x.y.z.0 255.255.255.0 serial1/1/3
> ip route x.y.z.0 255.255.255.0 serial1/0/0/12:0
>
> The customer works but still has the problem where all the traffic sacks one
> line inbound to their 28xx from our 7507.  So all we accomplished here
> really was pre-build a multilink PPP bundle but just change the encaps for
> each serial interface to PPP instead of HDLC.
>
> Then I thought what I'd do is add each serial interface to the multilink
> bundle using:
>
> Int Serial1/1/0
>    ppp multilink
>    ppp multilink group 1
> Int Serial1/1/3
>    ppp multilink
>    ppp multilink group 1
> Int Serial1/0/0/12:0
>    ppp multilink
>    ppp multilink group 1
>
> That is when the fun stopped (no packets routed at all). I did get this
> message on the console:
>
> Jul 30 09:03:09 MDT: %RP_MLP-5-LINKTYPEMISMATCH: Link(Serial1/0/0/12:0)
> added, Bundle(Multilink1) may not be distributed
>
> Not sure what this means.
>
> So I assume what I should have done in addition to adding the ppp multilink
> grouping to the serial interfaces is remove the static routes and replace
> them with this instead right?
>
> ip route x.y.z.0 255.255.255.0 Multilink1
>
> I haven't ever configured multilink PPP before but this is right isn't it?
>
> Thanks,
> CJ
>
>
> On 7/30/09 7:32 AM, "Matthew Huff" <mhuff at ox.com> wrote:
>
>   
>> Unless you do "per-packet" load-sharing (which you don't want to do since
>> it's cpu switched), the path is session based. If most of the traffic is
>> going from one source to one destination, it won't be load-shared. What do
>> the routing tables look like in both directions?
>>
>> ----
>> Matthew Huff       | One Manhattanville Rd
>> OTA Management LLC | Purchase, NY 10577
>> http://www.ox.com  | Phone: 914-460-4039
>> aim: matthewbhuff  | Fax:   914-460-4139
>>
>>
>>     
>>> -----Original Message-----
>>> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
>>> bounces at puck.nether.net] On Behalf Of Security Team
>>> Sent: Wednesday, July 29, 2009 11:24 PM
>>> To: cisco-nsp at puck.nether.net
>>> Subject: [c-nsp] Balancing T1's with CEF
>>>
>>> I rebooted a 7507 router that had a site connected with 3 T1's and now
>>> all
>>> the traffic is nailing one line instead of being distributed over all 3
>>> using the static routes/CEF.
>>>
>>> I did look at the Cisco troubleshooting tips but didn't see anything
>>> immensely helpful.  Here is a config snippet on the 7507 side (it's
>>> obviously nothing
>>> whizzy).
>>>
>>> Has anyone seen this before?  I did an ip clear cache and also tried
>>> doing a
>>> shut/no shut on each line individually on the 7507, but the traffic to
>>> the
>>> customer's
>>> 28xx router always sacks one line.  It seems like in the past I did
>>> some
>>> kind of clear on the 7507 and things got better, but I can't recall
>>> what
>>> that may have been.
>>>
>>> Thanks,
>>> CJ
>>>
>>> 7507 (all PA adapters on the same VIP) config. One T1 comes in on a
>>> chan DS3
>>> card breaking out individual T1¹s, and the other 2 T1¹s come in on a 4-
>>> port
>>> PA adapter T1 card. I¹m not using dCEF since I have never had good luck
>>> with
>>> it.
>>>
>>> ip cef
>>> !
>>> interface Serial1/0/0/12:0
>>>  bandwidth 1536
>>>  ip address x.x.x.x y.y.y.y
>>>  load-interval 30
>>>  no fair-queue
>>>  down-when-looped
>>>  no cdp enable
>>> !
>>> interface Serial1/1/0
>>>  bandwidth 1536
>>>  ip address x.x.x.x y.y.y.y
>>>  load-interval 30
>>>  no fair-queue
>>>  down-when-looped
>>>  no cdp enable
>>> !
>>> interface Serial1/1/3
>>>  bandwidth 1536
>>>  ip address x.x.x.x y.y.y.y
>>>  load-interval 30
>>>  no fair-queue
>>>  down-when-looped
>>>  no cdp enable
>>>
>>> _______________________________________________
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>>> https://puck.nether.net/mailman/listinfo/cisco-nsp
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>>>       
>
>
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>   

-- 
-----------------
Brian Raaen
Network Engineer
email: /braaen at zcorum.com/ <mailto:braaen at zcorum.com>
Telephone /678-507-5000x5574/