[dev] MPLS SWAP and POP configuration issue

Renato Westphal renato at opensourcerouting.org
Mon Jul 23 11:44:17 EDT 2018


On Fri, Jul 20, 2018 at 10:08 AM, Vijayalakshmi
<vijayalakshmi.marudhanayagam at veryxtech.com> wrote:
> Hi,
>
> I have found the issue in my configuration and now able to perform
> PUSH/SWAP/POP operations for MPLS via Linux Kernel.
>
> And I tested the same with FRR and here I am not sure about the
> configuration for popping a MPLS label.
>
> To add label via zebra,
> ip route 192.168.133.0/24 192.168.200.3 label 100
>
> To swap label via zebra,
> mpls lsp 100 192.168.123.4 200
>
> To remove label via zebra,
> ?????

For that you need to swap to the implicit-null label.

Example: mpls lsp 100 192.168.123.4 implicit-null

> Please let me know the configuration if anyone knows.
>
> Thanks,
> Vijayalaskhmi
>
> PS:
> The issue observed with Linux configuration of static route with nexthop as
> IP address works fine but nexthop as interface (dev) does not work.
>
> As the following works fine,
> 192.168.123.0/24  encap mpls  100 via 192.168.200.3 via 192.168.200.3 dev
> ens9
>
> but this does not work,
> 192.168.123.0/24  encap mpls  100 via 192.168.200.3 dev ens9

I guess you mean that this works:
192.168.123.0/24  encap mpls  100 via 192.168.200.3 dev ens9

But this doesn't work:
192.168.123.0/24  encap mpls  100 dev ens9

I think this has something to do with ARP resolution being triggered
only for IP packets in the Linux kernel. If ens9 is an ethernet
interface and you don't specify a nexthop address, the MPLS packets
will be sent to the ethernet broadcast address and dropped on the
other side (assuming there's only one). If ens9 is a point-to-point
interface then your second route should work normally.

Regards,
Renato.

> On 7/16/2018 7:15 PM, Vijayalakshmi wrote:
>
> Hi Kishore,
>
> Thanks for your reply.
>
> I tried the same with Linux MPLS via iproute2 configuration. Still the
> behavior is same.
> So it is clear that the issue is not with FRR.
>
> Let me fix the issue in my Linux kernel and get back to you if I need any
> support.
>
> Regards,
> Vijayalakshmi
>
> On 7/13/2018 9:45 PM, Kishore Aramalla wrote:
>
> Vijayalakshmi, Can you share your configuration.
>
>
>
> Best,
>
> Kishore
>
>
>
> From: dev <dev-bounces at lists.frrouting.org> On Behalf Of Vijayalakshmi
> Sent: Thursday, July 12, 2018 11:49 PM
> To: dev at lists.frrouting.org
> Subject: [dev] MPLS SWAP and POP configuration issue
>
>
>
> Hello,
>
> We are currently working with simulating a PE router in MPLS architecture.
> We run zebra and ldp with below configuration
> and facing issues in swapping and popping of label in zebra.
>
> In my MPLS table I have the following entries,
>
> zebra_2# show mpls table
>  Inbound                            Outbound
>    Label     Type          Nexthop     Label
> --------  -------  ---------------  --------
>       16      LDP    192.168.100.2         3
>       17   Static    192.168.100.2        18
>
> But still zebra is not swapping the label and also not forwarding the
> received traffic (inbound label 16/17) to the respective nexthop.
>
> Is there any special command to activate mpls configuration ?
> Can someone help us in a configuring zebra MPLS to pop label and swap label?
>
> Thanks,
> Vijayalakshmi
>
>
>
>
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>



-- 
Renato Westphal



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