Re: [j-nsp] Junos labeled-unicast announces unusable routes, certainly this is a bug
You CAN configure both AFI=1 SAFI=1 and AFI=1 SAFI=4 on the same BGP
session by specifying inet.3 for labeled-unicast routes:
family inet {
unicast;
labeled-unicast {
rib {
inet.3;
}
}
}
And redistributing LDP/RSVP routes from inet.3 makes perfect LSP stitching
through BGP-LU by label swapping.
Best Regards,
Krasi
On Mon, Jan 21, 2013 at 12:59 PM, Jeff Wheeler wrote:
> On Mon, Jan 21, 2013 at 4:27 AM, Alex Arseniev
> wrote:
> > Probably not what you want to hear at the moment but it "is working as
> > designed".
>
> No, it isn't.
>
> Junos BGP is announcing routes it knows, for sure, are invalid. It
> knows that because BGP is making up a wrong label (2^20-1) because it
> hasn't allocated one, and it can't announce the route without a label.
> This is an inexcusable bug that is very far from "working as
> designed."
>
> The documentation is wrong, you cannot configure both AFI=1 SAFI=1 and
> AFI=1 SAFI=4 on the same BGP session. If it worked as documented, the
> above behavior would not happen, and AFI=1 SAFI=1 would be available
> to use for these routes. That is not the case.
>
> --
> Jeff S Wheeler
> Sr Network Operator / Innovative Network Concepts
> ___
> juniper-nsp mailing list juniper-nsp@puck.nether.net
> https://puck.nether.net/mailman/listinfo/juniper-nsp
>
___
juniper-nsp mailing list juniper-nsp@puck.nether.net
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Re: [j-nsp] Junos labeled-unicast announces unusable routes, certainly this is a bug
On Mon, Jan 21, 2013 at 4:27 AM, Alex Arseniev wrote: > Probably not what you want to hear at the moment but it "is working as > designed". No, it isn't. Junos BGP is announcing routes it knows, for sure, are invalid. It knows that because BGP is making up a wrong label (2^20-1) because it hasn't allocated one, and it can't announce the route without a label. This is an inexcusable bug that is very far from "working as designed." The documentation is wrong, you cannot configure both AFI=1 SAFI=1 and AFI=1 SAFI=4 on the same BGP session. If it worked as documented, the above behavior would not happen, and AFI=1 SAFI=1 would be available to use for these routes. That is not the case. -- Jeff S Wheeler Sr Network Operator / Innovative Network Concepts ___ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp
Re: [j-nsp] Junos labeled-unicast announces unusable routes, certainly this is a bug
Probably not what you want to hear at the moment but it "is working as designed". There is nothing in BGP RFCs which mandate that BGP-LU _must_ consult LDP/RSVP/LFIB etc before announcing routes. To "force" BGP-LU to consult LDP/RSVP and automatically advertise/withdraw routes matching LSP endpoints, use combination of: 1/ "mpls traffic-engineering bgp-igp-both-ribs" (installs LDP/RSVP routes in inet.0 and in inet.3) 2/ BGP-LU export policy which exports LDP/RSVP routes as well as own loopback (all of them are in inet.0 as a result of [1] above) 3/ "resolve-vpn" under BGP LU family which causes received BGP-LU routes to install in both inet.0 and inet.3, for inet-vpn NH resolution HTH Thanks Alex - Original Message - From: "Jeff Wheeler" To: "juniper-nsp" Sent: Monday, January 21, 2013 12:25 AM Subject: [j-nsp] Junos labeled-unicast announces unusable routes,certainly this is a bug Dear List, The process of raising a PR with JTAC generally makes me want to scream, so I thought I would post first, and perhaps some kind Juniper person can input a PR# without me having to reproduce the problem again and jump through twenty hoops to later be told "working as designed." When configuring BGP labeled-unicast on Junos, you might think (like I hoped) that you could use LDP to create FECs and allocate labels, and then use those labels in your MP-BGP session. Unfortunately this does not work, and the basic reason is Junos BGP wants to allocate its own labels, and won't consult the LDP FEC table to see if any already exist for a given protocol next-hop which is being announced to the neighbor. Fine, so it wants to allocate its own labels. However, trying to avoid this behavior, I found it's pretty easy to get Junos to announce broken labeled-unicast routes that can never work, even though the receiving BGP speaker has no idea they are invalid. The receiver will just install the routes, forward traffic, and the traffic will get blackholed. This happens because Junos is trying to announce NLRI with no allocated labels (because layer-3 next-hop is not "self") and it can't announce them when labeled-unicast is configured, because the documentation is wrong, and you canNOT actually configure both AFI=1 SAFI=1 and AFI=1 SAFI=4 on the same BGP session. It simply does not work, and the Juniper documentation on this subject is incorrect. So what happens is, the announcing router knows it wants to announce a prefix, but it has no label stack for it, won't allocate one, and instead it just puts in label 1048575, or 2^20-1. This label is not in the LFIB, so when that router receives packets with that label, it doesn't pop the label and do a layer-3 look-up. Instead, it just discards the packets. Worse than that, the announcing router's `show route advertising-protocol bgp ` output is incorrect. It shows no label, even though it really is sending a label stack with 2^20-1. You have to go over to the receiving router to find this out. So this combination of documentation bugs and ridiculous Junos ability to announce labeled BGP routes that it knows for sure are invalid, is quite foolish, to say nothing of the fact that it won't just use FECs you already created using LDP. :/ Anyway, if you ever get labeled BGP routes with label 2^20-1, this might be why. Hopefully some kind Juniper folks will be willing to file some bugs on this for me, because I don't have a week to fight with JTAC about it. It is, however, very easy to reproduce the problem. :-) Thanks -- Jeff S Wheeler Sr Network Operator / Innovative Network Concepts ___ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp ___ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp
[j-nsp] Junos labeled-unicast announces unusable routes, certainly this is a bug
Dear List, The process of raising a PR with JTAC generally makes me want to scream, so I thought I would post first, and perhaps some kind Juniper person can input a PR# without me having to reproduce the problem again and jump through twenty hoops to later be told "working as designed." When configuring BGP labeled-unicast on Junos, you might think (like I hoped) that you could use LDP to create FECs and allocate labels, and then use those labels in your MP-BGP session. Unfortunately this does not work, and the basic reason is Junos BGP wants to allocate its own labels, and won't consult the LDP FEC table to see if any already exist for a given protocol next-hop which is being announced to the neighbor. Fine, so it wants to allocate its own labels. However, trying to avoid this behavior, I found it's pretty easy to get Junos to announce broken labeled-unicast routes that can never work, even though the receiving BGP speaker has no idea they are invalid. The receiver will just install the routes, forward traffic, and the traffic will get blackholed. This happens because Junos is trying to announce NLRI with no allocated labels (because layer-3 next-hop is not "self") and it can't announce them when labeled-unicast is configured, because the documentation is wrong, and you canNOT actually configure both AFI=1 SAFI=1 and AFI=1 SAFI=4 on the same BGP session. It simply does not work, and the Juniper documentation on this subject is incorrect. So what happens is, the announcing router knows it wants to announce a prefix, but it has no label stack for it, won't allocate one, and instead it just puts in label 1048575, or 2^20-1. This label is not in the LFIB, so when that router receives packets with that label, it doesn't pop the label and do a layer-3 look-up. Instead, it just discards the packets. Worse than that, the announcing router's `show route advertising-protocol bgp ` output is incorrect. It shows no label, even though it really is sending a label stack with 2^20-1. You have to go over to the receiving router to find this out. So this combination of documentation bugs and ridiculous Junos ability to announce labeled BGP routes that it knows for sure are invalid, is quite foolish, to say nothing of the fact that it won't just use FECs you already created using LDP. :/ Anyway, if you ever get labeled BGP routes with label 2^20-1, this might be why. Hopefully some kind Juniper folks will be willing to file some bugs on this for me, because I don't have a week to fight with JTAC about it. It is, however, very easy to reproduce the problem. :-) Thanks -- Jeff S Wheeler Sr Network Operator / Innovative Network Concepts ___ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp
