[Xorp-users] Wrong IP address used for GRE interface

[Ben Greear]

On 12/28/2011 05:22 AM, Andriy Senkovych wrote:
> Hello, xorp-users!
>
> I'm using Xorp 1.8.3 package on Debian for PIM-SM over GRE/IPSec. I
> used slightly modified default config. I use such tunnels to access
> both worker machines and data provider:

Use the latest code from github (1.8.5-WIP).  The problem should be
fixed there.

Thanks,
Ben

>
> The config file has the following interfaces section:
>
> interfaces {
>      restore-original-config-on-shutdown: false
>      interface cme-gw {
>          description: "Tunnel interface to data provider"
>          disable: false
>          default-system-config
>      }
>
>      interface cme-dev {
>          description: "Tunnel interface to worker machine"
>          disable: false
>          default-system-config
>      }
> }
>
> As a result I get the following interfaces configuration:
>
>> show interfaces
> cme-dev/cme-dev: Flags:<ENABLED,MULTICAST,POINTTOPOINT>  mtu 1476 speed unknown
>          inet 10.145.0.129 subnet 10.145.0.129/32 -->  10.145.129.63
>          inet 10.145.2.122 subnet 10.145.2.120/30 -->  10.145.2.122
>          physical index 5
> cme-gw/cme-gw: Flags:<ENABLED,MULTICAST,POINTTOPOINT>  mtu 1476 speed unknown
>          inet 10.145.0.129 subnet 10.145.0.129/32 -->  10.145.254.1
>          inet 10.145.2.222 subnet 10.145.2.220/30 -->  10.145.2.222
>          physical index 4
>
> My actual configuration for these interfaces is:
>
> $ ip a l
> 4: cme-gw:<POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP>  mtu 1476 qdisc
> noqueue state UNKNOWN
>      link/gre 10.145.0.129 peer 10.145.254.1
>      inet 10.145.2.222/30 scope global cme-gw
> 5: cme-dev:<POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP>  mtu 1476 qdisc
> noqueue state UNKNOWN
>      link/gre 10.145.0.129 peer 10.145.129.63
>      inet 10.145.2.122/30 scope global cme-dev
>
> Using config above I get the following pim interfaces configuration:
>
>> show pim interface
> Interface    State    Mode   V PIMstate Priority DRaddr          Neighbors
> cme-dev      UP       Sparse 2 DR              1 10.145.0.129            0
> cme-gw       UP       Sparse 2 DR              1 10.145.0.129            0
>
> And PIM_HELLO packets are sent with wrong parameters:
>
> [ 2011/12/28 13:07:18.8664 TRACE xorp_pimsm4 PIM ] pim_send: TX
> PIM_HELLO from 10.145.0.129 to 224.0.0.13 on vif cme-gw
> [ 2011/12/28 13:07:20.817323 TRACE xorp_pimsm4 PIM ] pim_send: TX
> PIM_HELLO from 10.145.0.129 to 224.0.0.13 on vif cme-dev
>
> Here you can see that xorp has chosen wrong IP address to send the
> packets (10.145.0.129 instead of 10.145.2.222 for cme-gw and
> 10.145.2.122 for cme-dev)
>
> I have similar(but working) environment to get data from another data
> provider. Its interfaces settings are:
>
> $ ip a l
> 4: tun247102:<POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP>  mtu 1476 qdisc
> noqueue state UNKNOWN
>      link/gre 192.168.247.29 peer 192.168.0.84
>      inet 10.100.247.102/30 scope global tun247102
> 5: rts-dev:<POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP>  mtu 1476 qdisc
> noqueue state UNKNOWN
>      link/gre 192.168.247.29 peer 192.168.133.10
>      inet 10.100.133.14/30 scope global rts-dev
>
>> show interfaces
> rts-dev/rts-dev: Flags:<ENABLED,MULTICAST,POINTTOPOINT>  mtu 1476 speed unknown
>          inet 10.100.133.14 subnet 10.100.133.12/30 -->  10.100.133.14
>          inet 192.168.247.29 subnet 192.168.247.29/32 -->  192.168.133.10
>          physical index 5
> tun247102/tun247102: Flags:<ENABLED,MULTICAST,POINTTOPOINT>  mtu 1476
> speed unknown
>          inet 10.100.247.102 subnet 10.100.247.100/30 -->  10.100.247.102
>          inet 192.168.247.29 subnet 192.168.247.29/32 -->  192.168.0.84
>          physical index 4
>
>> show pim interfaces
> Interface    State    Mode   V PIMstate Priority DRaddr          Neighbors
> rts-dev      UP       Sparse 2 DR              1 10.100.133.14           0
> tun247102    UP       Sparse 2 DR              1 10.100.247.102          1
>
>> From this I make the conclusion that xorp takes the first available
> configuration and uses is as a default. However as you can see this
> will work only when IP address of GRE tunnel is smaller than local IP
> address used to setup this GRE tunnel.
>
> I tried both using default-system-config and manual interfaces
> configuration but this didn't help.
>
> Is there any solution for this problem?
>


-- 
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com