BGP with wrong netmask on wan interface

[Alexander Zubkov]

But this works:

protocol static {
    route 192.168.2.0/24 via "test2";
    route 192.168.3.0/24 recursive 192.168.2.1;
}

bird> show route
192.168.0.0/16     dev dum1 [direct1 23:18:17] * (240)
192.168.1.0/24     dev test2 [direct1 23:10:42] * (240)
192.168.2.0/24     dev test2 [static1 23:10:42] * (200)
192.168.3.0/24     via 192.168.2.1 on test2 [static1 23:22:44] * (200)

I also succeeded with such bgp setup:

protocol static {
    route 192.168.2.0/24 via "test2";
#    route 192.168.3.0/24 recursive 192.168.2.1;
}

protocol bgp
{
    import all;
    local as 65002;
    source address 192.168.1.2;
    neighbor 192.168.2.1 as 65001;
    multihop 1;
}

bird> show route
192.168.0.0/16     dev dum1 [direct1 23:18:16] * (240)
192.168.1.0/24     dev test2 [direct1 23:10:41] * (240)
192.168.2.0/24     dev test2 [static1 23:10:41] * (200)
192.168.4.0/24     via 192.168.2.1 on test2 [bgp1 23:38:37] * (100/0)
[AS65001i]

bird> show route all 192.168.4.0/24
192.168.4.0/24     via 192.168.2.1 on test2 [bgp1 23:38:37] * (100/0)
[AS65001i]
    Type: BGP unicast univ
    BGP.origin: IGP
    BGP.as_path: 65001
    BGP.next_hop: 192.168.2.1
    BGP.local_pref: 100

If I have direct in BGP - bird ignores interface direct route and tries to
connect via dum1 interface. But multihop works.

On Wed, Nov 8, 2017 at 9:24 PM, Alexander Zubkov <green at qrator.net> wrote:

> Hi again,
>
> I think I've got you idea. Probably bird can not do "recursive" direct
> routes. For example I set up:
>
> Linux:
>
> 9: test2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
> state UP group default qlen 1000
>     link/ether 56:0a:42:5f:b3:46 brd ff:ff:ff:ff:ff:ff
>     inet 192.168.1.2/24 scope global test2
>        valid_lft forever preferred_lft forever
>
> 192.168.1.0/24 dev test2  proto kernel  scope link  src 192.168.1.2
> 192.168.2.0/24 dev test2  scope link
>
> bird have (no export to kernel):
>
> protocol static {
>     route 192.168.2.0/24 via "test2";
>     route 192.168.3.0/24 via 192.168.2.1;
> }
>
> And I see in bird no route for 192.168.3.0/24:
>
> bird> show route
> 192.168.1.0/24     dev test2 [direct1 23:10:42] * (240)
> 192.168.2.0/24     dev test2 [static1 23:10:42] * (200)
>
> If I add to Linux such device:
>
> 2: dum1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state
> UNKNOWN group default
>     link/ether ee:b2:97:43:3c:79 brd ff:ff:ff:ff:ff:ff
>     inet 192.168.100.1/16 scope global dum1
>        valid_lft forever preferred_lft forever
>
> And bird starts to route via it:
>
> bird> show route
> 192.168.0.0/16     dev dum1 [direct1 23:18:16] * (240)
> 192.168.1.0/24     dev test2 [direct1 23:10:41] * (240)
> 192.168.2.0/24     dev test2 [static1 23:10:41] * (200)
> 192.168.3.0/24     via 192.168.2.1 on dum1 [static1 23:18:16] * (200)
>
>
> On Wed, Nov 8, 2017 at 3:48 PM, Magnus Löfqvist <ml at vmi.se> wrote:
>
>> Hi again,
>>
>>
>>
>> If I use multihop (ie removing direct and gateway direct from config), it
>> will connect, but I get the imported routes with my internet gateway as
>> router.
>>
>>
>>
>> XX.XX.XX.0/27 via 10.6.24.82 dev wwan0  proto bird
>>
>>
>>
>> It should be
>>
>> XX.XX.XX.0/27 via 10.9.140.1 dev tap0  proto bird
>>
>>
>>
>> It doesn’t matter if I specified the source address and local address, it
>> seems always to try to send the traffic over wwan0 (external wan connection)
>>
>>
>>
>>
>>
>>
>>
>> Med vänlig hälsning / Best regards
>>
>> Magnus Löfqvist
>>
>>
>>
>> *VMI IT Services AB*
>>
>> *Head office:*
>>
>> Hantverksvägen 15
>>
>> 764 93 VÄDDÖ, SWEDEN
>>
>> *Visiting address:*
>>
>> Lilla Torget 1A
>>
>> 761 30 NORRTÄLJE, SWEDEN
>>
>> Tel +46 176 20 89 00 (02)
>>
>> Fax +46 176 20 89 19
>>
>>
>> E-mail: ml at vmi.se
>>
>>
>>
>> **** VMI E-mail disclaimer ****
>>
>>
>>
>> *The information in this e-mail is confidential and may be legally
>> privileged.*
>>
>> *It is intended solely for the addressee. Access to this email by anyone
>> else is unauthorized.*
>>
>> *If you are not the intended recipient, any disclosure, copying,
>> distribution or any action taken *
>>
>> *or omitted to be taken in reliance on it, is prohibited and may be
>> unlawful. Any opinions or *
>>
>> *advice contained in this e-mail are subject to the terms and conditions
>> expressed in the *
>>
>> *VMI General terms and conditions.*
>>
>>
>>
>> *Från:* green at highloadlab.com [mailto:green at highloadlab.com] *För *Alexander
>> Zubkov
>> *Skickat:* den 8 november 2017 11:52
>>
>> *Till:* Magnus Löfqvist <ml at vmi.se>
>> *Kopia:* bird-users at network.cz
>> *Ämne:* Re: BGP with wrong netmask on wan interface
>>
>>
>>
>> In that case it probably because you are using direct (not multihop) bgp
>> session and bird binds to the interface which have this address in its
>> direct network - wwan0. In that case only routes with dev wwan0 will be
>> applied. I think you want to use multihop bgp session. If you want to use
>> direct session and this address is accepted directly via tap0, than I think
>> specifying source address from tap0 in bgp session should work.
>>
>>
>>
>> On Wed, Nov 8, 2017 at 10:47 AM, Magnus Löfqvist <ml at vmi.se> wrote:
>>
>> Hi,
>>
>>
>>
>> Yes, you are correct.
>>
>> But we have routes for 10.9.140.0/22 (OpenVPN transport network)
>>
>>
>>
>> ip ro sh:
>>
>> default via 10.6.52.59 dev wwan0
>>
>> 10.0.0.0/8 dev wwan0  proto kernel  scope link  src 10.6.52.58
>>
>> 10.9.140.0/22 dev tap0  proto kernel  scope link  src 10.9.140.33
>>
>>
>>
>> Bird:
>>
>> bird> show route
>>
>> 0.0.0.0/0          via 10.6.52.59 on wwan0 [kernel1 09:43:55] * (10)
>>
>> 10.9.140.0/22      dev tap0 [direct1 09:44:12] * (240)
>>
>>
>>
>> So why are not BGP traffic to 10.9.140.1 going thru tap0 ?
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> Med vänlig hälsning / Best regards
>>
>> Magnus Löfqvist
>>
>>
>>
>> *VMI IT Services AB*
>>
>> *Head office:*
>>
>> Hantverksvägen 15
>>
>> 764 93 VÄDDÖ, SWEDEN
>>
>> *Visiting address:*
>>
>> Lilla Torget 1A
>>
>> 761 30 NORRTÄLJE, SWEDEN
>>
>> Tel +46 176 20 89 00 (02)
>>
>> Fax +46 176 20 89 19
>>
>>
>> E-mail: ml at vmi.se
>>
>>
>>
>> **** VMI E-mail disclaimer ****
>>
>>
>>
>> *The information in this e-mail is confidential and may be legally
>> privileged.*
>>
>> *It is intended solely for the addressee. Access to this email by anyone
>> else is unauthorized.*
>>
>> *If you are not the intended recipient, any disclosure, copying,
>> distribution or any action taken *
>>
>> *or omitted to be taken in reliance on it, is prohibited and may be
>> unlawful. Any opinions or *
>>
>> *advice contained in this e-mail are subject to the terms and conditions
>> expressed in the *
>>
>> *VMI General terms and conditions.*
>>
>>
>>
>> *Från:* green at highloadlab.com [mailto:green at highloadlab.com] *För *Alexander
>> Zubkov
>> *Skickat:* den 8 november 2017 10:16
>> *Till:* Magnus Löfqvist <ml at vmi.se>
>> *Kopia:* bird-users at network.cz
>> *Ämne:* Re: BGP with wrong netmask on wan interface
>>
>>
>>
>> Hi,
>>
>> You have:
>>
>> WAN (Mobile): 10.6.90.187 / 255.0.0.0
>>
>> OpenVPN interface (tap0):  10.9.140.33 / 255.255.252.0
>>
>>
>>
>> protocol bgp BGP1 from RR_LTE { neighbor 10.9.140.1 as 1; preference
>> 140;};
>>
>>
>>
>> So you are trying to reach 10.9.140.1. If you have no additional routes,
>> than this address falls into
>>
>> 10.6.90.187 / 255.0.0.0 network, i.e. WAN interface and will be routed
>> there.
>>
>>
>>
>> On Wed, Nov 8, 2017 at 8:20 AM, Magnus Löfqvist <ml at vmi.se> wrote:
>>
>> Hi,
>>
>>
>>
>> I have some mobile routers (connected over LTE) and with openvpn.
>>
>>
>>
>> Over the openvpn we are running a BGP to allow distribute some routes and
>> export routes.
>>
>>
>>
>> Some of the routers are having wrong netmask (255.0.0.0 instead of
>> 255.255.255.252).
>>
>> This seems to work (ie internet are working, and the openvpn connection
>> is established).
>>
>>
>>
>> But when we are trying to get the BGP connection up, it tries to send the
>> BGP connection over the WAN istead of openvpn connection.
>>
>> I guess that I have made some mistake in the config.
>>
>> It should take smaller path before matching the larger..
>>
>>
>>
>>
>>
>> WAN (Mobile): 10.6.90.187 / 255.0.0.0
>>
>> OpenVPN interface (tap0):  10.9.140.33 / 255.255.252.0
>>
>>
>>
>> Bird config:
>>
>>
>>
>> template bgp RR_LTE {
>>
>>         debug all;                                  # debug BGP
>>
>>         description "BIRD RR";
>>
>>         local as 1;                                 # the AS used by the
>> local BGP speaker
>>
>>         direct;
>>
>>         gateway direct;
>>
>>         import filter import_ATM;                                 # just
>> accept everything
>>
>>         export filter export_ATM;                                 # and
>> advertise it to all the neigbors
>>
>>         connect retry time 10;                      # reconnect try after
>> 10s
>>
>>         hold time 240;                               # hold time send in
>> BGP messages
>>
>> }
>>
>>
>>
>> protocol bgp BGP1 from RR_LTE { neighbor 10.9.140.1 as 1; preference
>> 140;};
>>
>>
>>
>> root at client1:/etc# tcpdump -ni wwan0 tcp port 179 and host 10.9.140.1
>>
>> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
>>
>> listening on wwan0, link-type EN10MB (Ethernet), capture size 65535 bytes
>>
>> 15:29:08.755188 IP 10.6.90.187.34974 > 10.9.140.1.179: Flags [S], seq
>> 1482209106, win 14600, options [mss 1460,sackOK,TS val 88007 ecr
>> 0,nop,wscale 8], length 0
>>
>> 15:29:11.762726 IP 10.6.90.187.45591 > 10.9.140.1.179: Flags [S], seq
>> 1681977930, win 14600, options [mss 1460,sackOK,TS val 88307 ecr
>> 0,nop,wscale 8], length 0
>>
>>
>>
>>
>>
>>
>>
>> Med vänlig hälsning / Best regards
>>
>> Magnus Löfqvist
>>
>>
>>
>>
>>
>>
>>
>
>
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