Re: MTU Issues

Hello Dear,

Yes it is a straight ethernet,and i have not changed anything on interface
configs on DS/PE facing to customer A,it is default to 1500,customer is
complaining that he can't transfer TCP files larger than 1492 from
A----B. But he says that he is able to transfer TCP files from B----A
with larger size than 1492. He says that there is no problem with backbone
carrier but with the customer carrier.

When i do a extended ping from mine DS/PE to customer B with a DF bit
set the ping sucess is 0% for larger MTU also i dont recieve any error
saying ICMP destination unreacheable messages,

Generally when a MTU is high and DF is set the intermediate router send a
notification ICMP destination unreacheable messages,but in my case no
feedback except success rate.

On Tue, Oct 6, 2009 at 10:36 PM, Bryan Bartik <bbartik_at_ipexpert.com> wrote:

> Well make sure it raised on ALL the core links. Is the link between the CE
> and PE straight Ethernet? 1500 should be fine there.
>
>
> On Tue, Oct 6, 2009 at 12:32 PM, mike arnold <haynessmith70_at_gmail.com>wrote:
>
>> 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
>>>>
>>>>
>>>> Blogs and organic groups at http://www.ccie.net
>>>>
>>>> _______________________________________________________________________
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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/>
>>>
>>
>>
>
>
> --
> Bryan Bartik
> CCIE #23707 (R&S), CCNP
> Sr. Support Engineer - IPexpert, Inc.
> URL: http://www.IPexpert.com <http://www.ipexpert.com/>

Blogs and organic groups at http://www.ccie.net
Received on Tue Oct 06 2009 - 23:01:37 ART