[j-nsp] MTU issue

[john doe]

Hi


So I have some kind of MTU problem.


The setup is a Cisco on one side and a MX one the other. Between them are a
10G wavelength. MPLS, RSVP is running and the ERO of my LSP is taking the
direkt path between the boxes. All interfaces on both sides are well above
8000 in MTU, MPLS MTU on Cisco and Juniper side is also above 8000. Both
boxes are PE routers. If I do a ping sweep from other routers connected to
Cisco-router aswell as juniper-router to respective router both can show a
sweep result that is above 8000, but not the path between them.


If I make a ping sweep from the juniper to the Cisco on a LSP taking the
direkct path I get this:


100! 5052. 2576. 1340! 2580. 1960. 1652. 1496! 1576. 1536. 1516! 1528!
1540. 1536. 1532!

--- lsp ping sweep result---

Maximum Transmission Unit (MTU) is 1532 bytes


What could cause the Low MTU?


Johan
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[Mikael Abrahamsson]

Post by john doe
The setup is a Cisco on one side and a MX one the other. Between them are a
10G wavelength. MPLS, RSVP is running and the ERO of my LSP is taking the
What could cause the Low MTU?

My guess is that it's actually not a "wavelength" but someones packet
network in between and they're just calling it a "wavelength". So call the
"wavelength" provider and ask them what MTU they support.

[Aaron1]

Last year I tried to set mtu to 16000 between (2) MX960’s that were connected with DWDM ciena... I was dropping packets and found out that the ciena DWDM had a mtu limit. I set my mx960’s to something around 9200 and was ok then

Not sure what your problem is but thought I would share that DWDM sometimes has an MTU limit

Aaron

Post by john doe
The setup is a Cisco on one side and a MX one the other. Between them are a
10G wavelength. MPLS, RSVP is running and the ERO of my LSP is taking the
What could cause the Low MTU?

My guess is that it's actually not a "wavelength" but someones packet network in between and they're just calling it a "wavelength". So call the "wavelength" provider and ask them what MTU they support.
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[Mikael Abrahamsson]

Post by Aaron1
Not sure what your problem is but thought I would share that DWDM
sometimes has an MTU limit

It depends what it is.

https://www.cisco.com/c/en/us/td/docs/routers/ncs4200/configuration/guide/chassis/ch-config-ncs4200-book/ch-config-ncs4200-book_chapter_01000.pdf

page 4

"The standard 10 GbE LAN has a data rate of 10.3125 Gbps. In the OTU1e and
OTU2e mapping schemes, the full 10.3125 Gbit/s is transported including
the 64B/66B coded information, IPG, MAC FCS, preamble, start-of-frame
delimiter (SFD) and the ordered sets (to convey fault information)."

So with this kind of transport network, you should not have MTU limit
because it's bit transparent.

But then again, this is not "DWDM wave", this is a transport network of
capacity. It can run at multiple speeds, and the whole talk about "waves"
is typically a misnomer because it seldom is.

[john doe]

I talked to my supplier and they say that there is no MTU settings or
limitations on their wavelength service. I have other wavelengths from the
same supplier that works as expected so maybe it's not on their end.

Johan

Post by Mikael Abrahamsson

Post by john doe
The setup is a Cisco on one side and a MX one the other. Between them

are a

Post by john doe
10G wavelength. MPLS, RSVP is running and the ERO of my LSP is taking the
What could cause the Low MTU?

My guess is that it's actually not a "wavelength" but someones packet
network in between and they're just calling it a "wavelength". So call the
"wavelength" provider and ask them what MTU they support.
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[Enoch Nyatoti via juniper-nsp]

Hi,
Do you have a loopback filter with icmp rate limiting on the MX router? If so try to deactivate and test.

Best regards
E.N.



On Monday, October 22, 2018, 10:21:57 PM GMT+2, john doe <***@gmail.com> wrote:

I talked to my supplier and they say that there is no MTU settings or
limitations on their wavelength service. I have other wavelengths from the
same supplier that works as expected so maybe it's not on their end.

Johan

Post by Mikael Abrahamsson

Post by john doe
The setup is a Cisco on one side and a MX one the other. Between them

are a

Post by john doe
10G wavelength. MPLS, RSVP is running and the ERO of my LSP is taking the
What could cause the Low MTU?

My guess is that it's actually not a "wavelength" but someones packet
network in between and they're just calling it a "wavelength". So call the
"wavelength" provider and ask them what MTU they support.
--

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[Nikos Leontsinis]

Check CoS config and the Mpc you are using. Is there fusion in the picture?

Post by Enoch Nyatoti via juniper-nsp
Hi,
Do you have a loopback filter with icmp rate limiting on the MX router? If so try to deactivate and test.
Best regards
E.N.
I talked to my supplier and they say that there is no MTU settings or
limitations on their wavelength service. I have other wavelengths from the
same supplier that works as expected so maybe it's not on their end.
Johan

Post by Mikael Abrahamsson

Post by john doe
The setup is a Cisco on one side and a MX one the other. Between them

are a

Post by john doe
10G wavelength. MPLS, RSVP is running and the ERO of my LSP is taking the
What could cause the Low MTU?

My guess is that it's actually not a "wavelength" but someones packet
network in between and they're just calling it a "wavelength". So call the
"wavelength" provider and ask them what MTU they support.
--

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[Alain Hebert]

    Well,

    We had the same issue when switching one of our so called
"wavelength" from L2 (1536) to MPLS/Jumbo (9216).

    After the usual Level 1 incompetence, we got tired and asked to
bumped it to engineering, we found out they had some active booster that
had a limitation of 2000 bytes per packet.

    There was an active/passive MUX, from FS.com, that created some
headache for us too...

-----
Alain Hebert ***@pubnix.net
PubNIX Inc.
50 boul. St-Charles
P.O. Box 26770 Beaconsfield, Quebec H9W 6G7
Tel: [phone] http://www.pubnix.net Fax: [phone]

Post by john doe
I talked to my supplier and they say that there is no MTU settings or
limitations on their wavelength service. I have other wavelengths from the
same supplier that works as expected so maybe it's not on their end.
Johan

Post by Mikael Abrahamsson

Post by john doe
The setup is a Cisco on one side and a MX one the other. Between them

are a

Post by john doe
10G wavelength. MPLS, RSVP is running and the ERO of my LSP is taking the
What could cause the Low MTU?

My guess is that it's actually not a "wavelength" but someones packet
network in between and they're just calling it a "wavelength". So call the
"wavelength" provider and ask them what MTU they support.
--

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