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| carpediumtoday 2004-11-05, 11:07 am |
| Curious about someting. I have a situation coiming up in the next month that requires a frame relay circuit and a cisco on one side and a bay router on the other. On the Cisco, when it comes to LMI, will I need to match the lmi type on the bay (ansi) or the lmi type from the provider switch (cisco)? I think that I will match with the provider router, since they will be the ones exchanging lmi, but since there is a bay router on the other side, I didnt know for sure. Thank you for your help. | |
| The Reamer 2004-11-05, 11:38 am |
| It should match the switch. | |
| Mat P 2004-11-05, 11:51 am |
| Hint - What does LMI stand for??? | |
| carpediumtoday 2004-11-05, 5:42 pm |
| Thanks Reamer. | |
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| What about me....
LMI - Local Managemet Interface, with the key bit to your question being local. I was hoping to give you a way of understanding it rather than memorising | |
| carpediumtoday 2004-11-06, 6:48 pm |
| I know what LMI stands for, but I hardly see the connecting switch being local. Local would be my router only, in my view. I know the theory, I just needed that to be more clear. | |
| Pmwpaul 2004-11-08, 11:21 am |
| Your service provider doesn't have to have the same protocols after the local switch. So... provide proper frame relay and lmi info for communicating with the switch.
Another way of looking at it is to provide compatability up to the DEMARKATION point. That is also your responsibility line. If your service provider is monitoring your line, it is only up to their switch that they usually check. | |
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| Then only thing that HAS TO MATCH between the bay router you have and the cisco router would be the encapsulation type. LMI, as others have stated, only have to match between the router and the local switch. LMI can be different on the cisco as opposed to the Bay router. Again, only encapsulation matters. | |
| Just Visiting 2004-12-15, 6:28 am |
| Not so sure Dude is correct. You can have frame-relay at one end and ATM at the other so what makes you think the encapsulation matters? The frame-relay rfc only covers router to frame switch, so whatever happens after that is of no concern. Out of good practice I have never mismatched encapsulation or LMI types but I don't believe it matters.
-JV | |
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| No disrespect intended here JV, but I tried it twice to make sure. If the cisco router on one side is sending packets encapsulated with "cisco frame-relay", how is his bay networks router going to decapsulate it if it doesnt know anything about "cisco frame-relay" encapsulation, since its a "cisco" proprietery encapsulation method. Thats why both have to be "ietf frame-relay" in his/her case. | |
| Just Visiting 2004-12-29, 6:59 am |
| It is because the directly connected frame switch owned by the provider also understands cisco encapsulation and takes care of that. The frame-relay rfc only covers from your site to the carrier switch. What is done in their cloud (usually ATM)is up to the carrier. The frame switch at the destination end will take care of doing the encapsulation so your far end will understand.
-JV | |
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| Believe me, the carrier doesnt care about your encapsulation. They dont care if your data gets to the other end or not. They only care about connecting to your site and exchanging lmi and thats it. Can you imagine how much overhead it would put on thier router if it had to "convert" encapsulation types? One, its not possible and Two, they wouldnt do that even if it was.
Here is what I invite you to do. Telnet into one of your routers on a remote site. Go in and change the encapsulation type to something different from what you are using on the central site. See if you dont get dropped. | |
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| In fact, if you call a carrier, ask them what they usually use for setting up a circuit. They are going to tell you, in thier words, how many "channels" or timeslots to use and also the "startup protocol", which in tech terms means LMI. Funny, because they dont know anything about encapsulation type. In fact, if you mention that to them, they think you are talking about thier "startup protocol", and we all know that encapsulation type and lmi type are not the same. | |
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| Here is a cut and paste from Sybex CCNP Remote Access. I hate to use Sybex, but its what was handy.
"Cisco is the default encapsulation, which means that you have another
Cisco router on the remote end with which your router will communicate.
You will use the IETF encapsulation when communicating with a remote
router that is not a Cisco device."
Do you see anything in there at all about the carrier router??? | |
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| quote:
It is because the directly connected frame switch owned by the provider also understands cisco encapsulation and takes care of that.
Hey, one more question for you JV. This is your quote above. What if the carrier didnt have a Cisco router in place? Obviously, it couldnt understand "cisco frame-relay" then.
Its like this, if Im going to give you some data by talking to you, I must speak English to you. If I speak Zambulie to you, you wouldnt understand. So Me, being the central site, talking data to You, being remote site, have to understand what language Im talking so that data can be transferred from me to you. | |
| Just Visiting 2005-01-04, 6:12 am |
| Just one final post on this from me because it is important people reading come away with the facts. Point to Points require encapsulation match on both your routers (the end points). With frame-relay it is between your router and the frame-relay SWITCH (not a router) so your routers may have different encapsulation types at the end points of a PVC.
Just because the Cisco LMI type was developed by Cisco, it doesn't mean no one else can emmulate it. In fact they do, but the carriers don't necessarily call it Cisco LMI. They use another name. Same thing with CDP. Many switch manufaturers now "talk" CDP, but they call it something else (HP and Foundry come to mind).
Having said all this I still say it is good form to match LMI type on all sites. I just want it understood it is not a technical necessity.
-JV (aka Yankee) | |
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| Im curious JV, did you actually TRY to do what I asked? Did you actually try to telnet in and try to mismatch the encapsulation on the frame-relay to see if it would drop you or not? | |
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| By the way JV, when Cisco developes something, its usually proprietary. | |
| centillian2000 2005-03-22, 6:54 pm |
| maybe i can straighten this up.. dude is confuzed.
you are not on a point to point link. you are connected to a cloud. that stated, it is POSSIBLE that your cisco router would use frame relay encapsulation, and your bay router would run ATM. and the LMI type could be different on both sides (maybe a different config on the providers frame - switch). For instances, say you had a nortel BCN, with an OC3 running ATM, and had 2000 remote sites, the one site you speak of is connected to that OC3, by way of a frame relay PVC. in the provider cloud, at one point, that convert from frame realy to atm. we do this at my work. i think this discussion was old, but for anyone who is reading this... | |
| Just Visiting 2005-03-23, 6:31 am |
| Thanks for attempting to straighten him out. I tried but obviously was getting no where and thought it was doing more harm then good so I stopped.
-JV | |
| The Reamer 2005-03-24, 1:54 pm |
| Let me see if I can help with discussion. It looks to me like there is confusion in what is meant by "the other side." Some use this to mean from one customer edge router (CE) to another CE. Others are using it to mean from the CE to the providers edge (PE).
I work for an ISP and we use IETF instead of cisco because there is a mixture of routers within our core. Our customers are instructed to set the encapsulation to the same on their routers. From within our cloud, on our PE router, to the CE the encapsulation has to match. The only thing the switch is really concerned with is the LMI type and DLCI.
So depending on your perspective, the encapsulation might not match from CE to CE if they connect to different PE routers, but that would depend on the carrier. If the only thing between them is Frame switch, then they have to match on both ends.
HTH,
Reamer | |
| darthfeces 2005-03-24, 2:17 pm |
| w / at&t we just run ppp over our 4 backup t1's |
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