Re: MTU Issues

Hello,

The link on distribution PE facing to customer A is default to MTU 1500,on
distribution to core it is mpls mtu 1524 and SVI on core facing to ISP is
default to 1500 on ethernet.

On Tue, Oct 6, 2009 at 10:15 PM, Bryan Bartik <bbartik_at_ipexpert.com> wrote:

> Did you raise the MTU on the other links?
>
> On Tue, Oct 6, 2009 at 12:02 PM, mike arnold <haynessmith70_at_gmail.com>wrote:
>
>> Hello Dear's
>>
>> Topology:
>>
>> Its a Carrier Supporting Carrier Scenario.
>>
>> A------DS/PE---CORE/P---ISP/PE--P---ISP/PE------B
>>
>> AS per above topology,am not able to transfer files with MTU frame size
>> above 1492 though the MTU configured on interface is 1500.The interface on
>> which customer A is connected MTU is default to 1500.The link between
>> DS/PE---CR/PE is mpls enabled i have configured the MTU size to 1524 to
>> carry labels of MPLS as recommended by cisco.
>>
>> When i do extnded ping from DS/PE above MTU size of 1492 with even DF bit
>> not set am not able to ping customer end (B),
>>
>> AND also i tried with DF bit set am not able to recieve any notifications
>> ICMP destination unreacheable messages.
>>
>> The file transfer from customer B with packet size above 1492 are received
>> by customer A but when the connection are initiated through customer A
>> they
>> are not.
>>
>> Within an enterprise it works with larger MTU size when tried to ping from
>> Distribution loopback to core loopback.How can i troubleshoot it is a
>> problem through my end or from the ISP.
>>
>> The link between core and ISP is back to back VRF connected via a layer 2
>> trunk.The ISP is creating a sub-interfaces on his 3800 router with
>> encapsulation and vlan number.AND on Core am creating a SVI with a same
>> vlan
>> number and ip address within the subnet.
>>
>> Each customer VRF for exampl:(Customer A) is associated with SVI virtual
>> interface on 6500(core)and traffic is passed to customer B.On SVI the MTU
>> is
>> default to 1500.
>>
>> BGP is routing protocol between CORE nd ISP.
>>
>> ON 3800 router (ISP End)
>> int gig0/0
>> no shut
>> no ip add
>>
>> int gig0/0.1
>> no shut
>> encapsulation dot1q 50
>> ip vrf forwarding XX
>> ip add 10.10.10.1 255.255.255.254
>>
>> ON MY END (CORE)
>> int gig5/1
>> switchport trunk encapsulation dot1q
>> switch mode trunk
>>
>> int vlan 50
>> ip vrf forwarding customer A
>> ip add 10.10.10.2 255.255.255.254.
>>
>> Thanks
>>
>>
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>>
>>
>>
>>
>>
>
>
> --
> Bryan Bartik
> CCIE #23707 (R&S), CCNP
> Sr. Support Engineer - IPexpert, Inc.
> URL: http://www.IPexpert.com <http://www.ipexpert.com/>

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Received on Tue Oct 06 2009 - 22:32:11 ART