Re: [vpp-dev] Query on VPP behaviour when IP from same subnet configured on plain and vlan interface

[bindiya Kurle]

Hi Ole,
Thanks for pointers for IPv6.

"Are you saying that the following works in Linux:"
[Bindiya] : Yes .Little change to your configuration below

192.0.2.1/24 -> Eth0
192.0.2.2/24 -> *Eth0.111*(vlan interface on eth0)



Or are you saying that Linux ignores the second entry and just uses the
first entry in the FIB?
[Bindiya ] : in this config yes , ping to destination IP 192.0.2.10(VLAN)
will go on plain interface (ARP resolved on plain interface)
In VPP arp will be generated on VLAN interface

 What then happens with the 192.0.2.2 address?
[Bindiya ] : wrt Linux 192.0.2.2 it will be ignored
   wrt VPP it will use vlan interface.

workaround will be to add static route.
As suggested earlier this seems to be invalid scenario. Thanks for the help
.

Regards,
Bindiya
---

Are you saying that the following works in Linux:

192.0.2.1/24 -> Eth0
192.0.2.2/24 -> Eth1

Where Eth0 and Eth1 are connected to the same L2.

Or are you saying that Linux ignores the second entry and just uses the
first entry in the FIB?
What then happens with the 192.0.2.2 address?


Below is the configuration that test case was doing:
.
13.0.0.200 ---|GigabitEthernet1/0/0 (plain
interface)13.0.0.2
  |
GigabitEthernet1/0/0.111(vlan interface)13.0.0.5packet to send out
destination IP (13.0.0.200)

In this configuration , Ping to the same destination IP(IP: 13.0.0.200)
works (in Linux)as kernel pick up the plain interface route since that is
the 1st route in its routing table.

But VPP ends up requesting ARP(IP: 13.0.0.200) on a VLAN interface which
fails since the ARP is reachable only via the plain interface.



Regards,

Bindiya



On Tue, May 15, 2018 at 1:00 PM, Ole Troan  wrote:

> Hi Bindiya,
>
> > Linux had allowed this configuration and test cases which were running
> on Linux failed on VPP.
> > The reason why it had passed is that linux always picks up the 1st entry
> that gets added in routing table i.e. plain interface while in VPP fib
> entry always return last interface that get added. Hence was curious if
> this was intentional?
>
> Are you saying that the following works in Linux:
>
> 192.0.2.1/24 -> Eth0
> 192.0.2.2/24 -> Eth1
>
> Where Eth0 and Eth1 are connected to the same L2.
>
> Or are you saying that Linux ignores the second entry and just uses the
> first entry in the FIB?
> What then happens with the 192.0.2.2 address?
>
> > Your point "While IPv6 notionally has support for that" is this from the
> RFC, could you please direct me to that?
>
> Look for "inbound load balancing" and "same link" in RFC4861 and RFC4862.
> It is pretty hand-wavy. E.g. it could be implemented as a new virtual
> interface hiding the two underlaying physical interfaces.
>
> Cheers,
> Ole
>

Re: [vpp-dev] Query on VPP behaviour when IP from same subnet configured on plain and vlan interface

[Ole Troan]

Hi Bindiya,

> Linux had allowed this configuration and test cases which were running on 
> Linux failed on VPP.
> The reason why it had passed is that linux always picks up the 1st entry that 
> gets added in routing table i.e. plain interface while in VPP fib entry 
> always return last interface that get added. Hence was curious if this was 
> intentional?

Are you saying that the following works in Linux:

192.0.2.1/24 -> Eth0
192.0.2.2/24 -> Eth1

Where Eth0 and Eth1 are connected to the same L2.

Or are you saying that Linux ignores the second entry and just uses the first 
entry in the FIB?
What then happens with the 192.0.2.2 address?

> Your point "While IPv6 notionally has support for that" is this from the RFC, 
> could you please direct me to that?

Look for "inbound load balancing" and "same link" in RFC4861 and RFC4862.
It is pretty hand-wavy. E.g. it could be implemented as a new virtual interface 
hiding the two underlaying physical interfaces.

Cheers,
Ole

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Re: [vpp-dev] Query on VPP behaviour when IP from same subnet configured on plain and vlan interface

[bindiya Kurle]

Hi Ole,

Linux had allowed this configuration and test cases which were running on
Linux failed on VPP.
The reason why it had passed is that linux always picks up the 1st entry
that gets added in routing table i.e. plain interface while in VPP fib
entry always return last interface that get added. Hence was curious if
this was intentional?

Your point "While IPv6 notionally has support for that" is this from the
RFC, could you please direct me to that?

Thanks,
Bindiya


On Tue, May 15, 2018 at 12:32 AM, Ole Troan  wrote:

> >  Thanks for the response. Any plans to differ this behaviour in future
> to support multiple interfaces in the same subnet?
>
> How do you intend for that to work?
> (While IPv6 notionally has support for that, as far as I know no
> implementations support it.
>



> Best regards,
> Ole
>
>
>
> 
>
>

Re: [vpp-dev] Query on VPP behaviour when IP from same subnet configured on plain and vlan interface

[Ole Troan]

>  Thanks for the response. Any plans to differ this behaviour in future to 
> support multiple interfaces in the same subnet?

How do you intend for that to work?
(While IPv6 notionally has support for that, as far as I know no 
implementations support it.

Best regards,
Ole



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Re: [vpp-dev] Query on VPP behaviour when IP from same subnet configured on plain and vlan interface

[bindiya Kurle]

Hi  Neale,

 Thanks for the response. Any plans to differ this behaviour in future to
support multiple interfaces in the same subnet?

Regards,
Bindiya

On Mon, May 14, 2018 at 5:15 PM, Neale Ranns (nranns) 
wrote:

>
>
> VPP does not support multiple interfaces in the same subnet.
>
> Your scenario will be a configuration error once:
>
>   https://gerrit.fd.io/r/#/c/8057/
>
> is committed.
>
>
>
> /neale
>
>
>
> *From: * on behalf of bindiya Kurle <
> bindiyaku...@gmail.com>
> *Date: *Monday, 7 May 2018 at 07:27
> *To: *"vpp-dev@lists.fd.io" 
> *Subject: *[vpp-dev] Query on VPP behaviour when IP from same subnet
> configured on plain and vlan interface
>
>
>
> *Hi,*
>
>
>
> 13.0.0.200 ---|GigabitEthernet1/0/0 (plain
> interface)13.0.0.2
>
>   |
> GigabitEthernet1/0/0.111(vlan interface)13.0.0.5packet to send out
> destination IP (13.0.0.200)
>
>
>
> Fig 1.
>
>
>
>
>
> I am trying to configure two IP’s belonging to same subnet on plain and a
> VLAN interface(refer fig 1).While sending a packet, the ip4-lookup node is
> fetching the dpoi_index pertaining to the VLAN interface which in-turn
> gives the software index to VLAN interface in lookup.
>
> If I try same scenario on Linux ,ping to the same destination IP(IP:
> 13.0.0.200) works as kernel pick up the plain interface route since that
> is the 1st route in its routing table.
>
>
>
> *FIB table entry: *
>
> 13.0.0.2/32  pmtu: 0
>
>   unicast-ip4-chain
>
>   [@0]: dpo-load-balance: [proto:ip4 index:12 buckets:1 uRPF:16 to:[0:0]]
>
> [0] [@2]: dpo-receive: 13.0.0.2 on GigabitEthernet1/0/0
>
> 13.0.0.5/32  pmtu: 0
>
>   unicast-ip4-chain
>
>   [@0]: dpo-load-balance: [proto:ip4 index:17 buckets:1 uRPF:22 to:[0:0]]
>
> [0] [@2]: dpo-receive: 13.0.0.5 on GigabitEthernet1/0/0.111
>
> 13.0.0.200/32  pmtu: 0
>
>   UNRESOLVED
>
>
>
> Questions :
>
> 1. Is there any specific reason why VPP always returns last entry added
> for that prefix instead of 1st entry? Can Vpp behaviour be made similar to
> Linux kernel Behaviour?
>
>
>
>
>
> Regards,
>
> Bindiya
>
>
>
> 
>
>

Re: [vpp-dev] Query on VPP behaviour when IP from same subnet configured on plain and vlan interface

[Neale Ranns]

VPP does not support multiple interfaces in the same subnet.
Your scenario will be a configuration error once:
  https://gerrit.fd.io/r/#/c/8057/
is committed.

/neale

From:  on behalf of bindiya Kurle 
Date: Monday, 7 May 2018 at 07:27
To: "vpp-dev@lists.fd.io" 
Subject: [vpp-dev] Query on VPP behaviour when IP from same subnet configured 
on plain and vlan interface

Hi,

13.0.0.200 ---|GigabitEthernet1/0/0 (plain 
interface)13.0.0.2
  | 
GigabitEthernet1/0/0.111(vlan interface)13.0.0.5packet to send out 
destination IP (13.0.0.200)


Fig 1.


I am trying to configure two IP’s belonging to same subnet on plain and a VLAN 
interface(refer fig 1).While sending a packet, the ip4-lookup node is fetching 
the dpoi_index pertaining to the VLAN interface which in-turn gives the 
software index to VLAN interface in lookup.
If I try same scenario on Linux ,ping to the same destination IP(IP: 
13.0.0.200) works as kernel pick up the plain interface route since that is the 
1st route in its routing table.



FIB table entry:

13.0.0.2/32  pmtu: 0

  unicast-ip4-chain

  [@0]: dpo-load-balance: [proto:ip4 index:12 buckets:1 uRPF:16 to:[0:0]]

[0] [@2]: dpo-receive: 13.0.0.2 on GigabitEthernet1/0/0

13.0.0.5/32  pmtu: 0

  unicast-ip4-chain

  [@0]: dpo-load-balance: [proto:ip4 index:17 buckets:1 uRPF:22 to:[0:0]]

[0] [@2]: dpo-receive: 13.0.0.5 on GigabitEthernet1/0/0.111

13.0.0.200/32  pmtu: 0
  UNRESOLVED

Questions :
1. Is there any specific reason why VPP always returns last entry added for 
that prefix instead of 1st entry? Can Vpp behaviour be made similar to Linux 
kernel Behaviour?


Regards,
Bindiya