Re: MTU Issues

Yes, well the Fragmentation needed is a subset of the destination
unreachable so you are right. Nevertheless it seems like an MTU issue.
Whether you are using RR's or not shouldn't matter. Do you have a computer
that you can send pings from while running a capture? It shouldn't be too
hard.

On Tue, Oct 6, 2009 at 1:40 PM, mike arnold <haynessmith70_at_gmail.com> wrote:

>
> Helllo,
> Though i have a RR connected to my core and RR is peering MPBGP with core
> and DS,but since my DS and core are directly connected so it does'nt make
> such difference for presence of ip next-hopself command on core as my all
> loopback are advertised in IGP (OSPF,)
>
> One thing to highlight mine core and DS is 10gig X2 module,
>
> Any more hints from any body,it's a strange issue for me,what else i can do
> here.
>
>
>
> On Tue, Oct 6, 2009 at 11:21 PM, mike arnold <haynessmith70_at_gmail.com>wrote:
>
>> i dont have packet capture,this message i won't be getting on my telnet
>> session.i have read on internet i shld receive this
>> message.
>>
>> Customer complaints that TCP files transfered from B to A with MTU 1500
>> has no problem but from A to B it can't above 1492. He says that the problem
>> is with the customer carrier not with the backbone carrier.
>>
>> How the above para can be possible,traffic is passsing through the same
>> interface as such what it is passing from to A to B
>>
>> On Tue, Oct 6, 2009 at 11:10 PM, Bryan Bartik <bbartik_at_ipexpert.com>wrote:
>>
>>> You won't get a Destination Unreachable, you will get a Fragmentation
>>> Needed and Don't Fragment Bit Set. Did you get a packet capture? Who is
>>> sending you the message?
>>>
>>>
>>> On Tue, Oct 6, 2009 at 1:01 PM, mike arnold <haynessmith70_at_gmail.com>wrote:
>>>
>>>> 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
>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________________________________
>>>>>>>> Subscription information may be found at:
>>>>>>>> http://www.groupstudy.com/list/CCIELab.html
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> 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/>
>>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> 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
Blogs and organic groups at http://www.ccie.net