MPLS MTU on FE interfaces with fixed interface MTU
What is the recommendation for setting MPLS MTU when the hardware does not permit the setting of the interface MTU:
PE-Edge-2(config)#int fastEthernet 0/0
PE-Edge-2(config-if)#mtu 1524
% Interface FastEthernet0/0 does not support user settable mtu.
The MPLS MTU could be changed with "mpls mtu 1524", but this gives the error:
PE-Edge-2(config-if)#mpls mtu 1524
*Dec 24 20:54:43.467: %TFIB-3-MPLS_MTU_SET: Setting mpls mtu to 1524 on FastEthernet0/0 which is higher than the interface mtu 1500 . This could lead to packet forwarding problems including packet drops.
Is it permissible to set the MPLS MTU greater than the interface MTU, as I thought that MPLS packets cannot not be fragmented, but rather simply dropped?
In this scenario, is the only solution to limit the size of inbound packets with something like "ip tcp adjust-mss 1476" to avoid any potential packet drops?
if your doing AToM then you have to change the mpls mtu in order to transport full frames over your backbone. I have the same issue with the mtu and setting the mpls mtu to 9196 while leaving the mtu at 1500 did not impact regular traffic at all but it did allow our l2vpn's to function correctly.
Similar Messages
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Pmtu and interface mtu,mpls mtu
Hi,
If pmtu work , do i need config interface mtu and mpls mtu on interface facing core,or p-p along the path.
thank you!Not necessarily. However, Path MTU is not guaranteed to work all the time because of things like firewalls and access-list. From a performance perspective, you will want the maximum possible MTU, which is what makes it adviseable to change the MTU (IP/MPLS).
-
Interface output file : tab limited vs flat file with fixed length
hey guys,
any idea on difference b/w to file type : flat file with fixed length or tab limited file
thanksTab Delimited:
Two Field are seperated by a TAB
eg. SANJAY SINGH
First field is First Name and Second is Sir Name.
Nth field will be after N -1 tab
Fixed Length:
Every field has a fixed starting position and length
eg. SANJAY SINGH
Here First field start from Position 1 and has lenght 10 and 2nd field start from 11th postion and has lenght 10.
Fixed Length -> The lenght of each field is fixed, while in tab delimited the lenght of field is not fixed but we know it ends when the Seperatot (Tab) is encountered. -
Dear All,
I got an ethernet backbone that do not support jumbo frame. The backbone connected my Cisco7206/NPE-G2 and Cisco7507 on each side.
The topology as below:
Cisco7206-Gi0/1<---Ethernet--->Cisco7507-F5/1/0.50 (I am using 802.1q sub-interface)
The config as below:
interface GigabitEthernet0/1
bandwidth 4000
ip address 10.86.40.2 255.255.255.252
no ip redirects
no ip proxy-arp
ip ospf network point-to-point
ip ospf cost 10
ip ospf mtu-ignore
load-interval 30
duplex full
speed 100
media-type rj45
negotiation auto
mpls label protocol ldp
mpls ip
mpls mtu 1508
end
interface FastEthernet5/1/0.50
encapsulation dot1Q 50
ip address 10.86.40.1 255.255.255.252
no ip redirects
no ip proxy-arp
ip ospf network point-to-point
ip ospf cost 10
ip ospf mtu-ignore
mpls label protocol ldp
tag-switching mtu 1508
tag-switching ip
end
interface FastEthernet5/1/0
description Trunk
no ip address
load-interval 30
full-duplex
end
The problem is when i using "ping vrf NM_TEST x.x.x.x size xxxx", the maximum size can only up to 1498byte. I have increase all of my switchs MTU to 1530, but also cannot ping with 1500byte. Is there any way can help to solve the problem?
Thanks for your kindly help!
RegardsHi Mohamed,
Its all about the implementation, with AToM, VPLS, MPLS TE, MVPN and any relatively new technology that is still being developed and enhanced you must take care about the vendors' implementations and which standards and RFCs is it complying with and to what level. I've seen codes that do fragmentation for AToM and codes that don't, codes that support out of order recovery and codes that don't. But in the end the RFCs and standards are there, whether you are using a code that supports what you need or not is your call.
Well, taking the AToM fragmentation and reassembly for example, I quote from "RFC 4623 Pseudowire Emulation Edge-to-Edge (PWE3) Fragmentation and Reassembly" : "Fragmentation takes place in the transmitting PE immediately prior to PW encapsulation, and reassembly takes place in the receiving PE immediately after PW decapsulation.", in brief it uses the B and E bits in the control word as well as the sequence number, and since the control word is imposed on the ingress PE and then processed on the egress PE, thus the ingress PE would be capable of fragmentation and the egress PE would be capable of reassembly, again its all about the code you are running.
Now to the 1530 MTU point, again I'll take an AToM case (more specifically EoMPLS), the Core MTU must be equal or greater than the summation of: Edge MTU (1500:IP) + Transport Header (14:Ethr + 4:assuming dot1q) + Control Word (4) + MPLS Label Stack (4:LDP + 4:VC), which gives a total of 1530. I believe that the reason behind choosing the value of 1530 in the new codes lies in the fact that it is the most common highest MTU seen in practice, although a value of 1534 is required if EoMPLS VLAN + TE FRR is used, but anyway the MPLS MTU is user settable up to 1580.
I hope that I've been informative.
BR,
Mohammed Mahmoud. -
"mpls traffic eng passive-interface" mapping on XR
Dears,
ON IOS for TE-InterAS ,the command "mpls traffic-eng passive-interface" is used on InterAS link which isn't running IGP so i am seeking for the equivlent command on XR but i can't find it so please advise what is the equivlent command on XR
ThanksHello Amr,
There is no equivalent command on IOS-XR. Are you trying to set up Inter-AS MPLS TE on XR? In IOS-XR, inter-AS tunnels are supported only by using verbatim path-options. Verbatim path-options are supported on both IOS and IOS-XR.
HTH,
Rivalino -
"mpls ip" global vs interface level command
What is the purpose of "mpls ip" global command? I think just enabling mpls on an interface by using "mpls ip" should be sufficient, but then what is the purpose of the global level command?
Usage Guidelines
Globally enabling MPLS forwarding does not enable it on the interfaces. You must enable MPLS forwarding on the interfaces separately.
MPLS forwarding of packets along normally routed paths (also called dynamic label switching) is enabled by this command. For a given interface to perform dynamic label switching, this switching function must be enabled.
The no form of this command stops dynamic label switching for all the interfaces regardless of the interface configuration; it also stops distribution of labels for dynamic label switching. However, the no form of this command does not affect the sending of labeled packets through the LSP tunnels.
link:
http://www.cisco.com/c/en/us/td/docs/optical/cpt/r9_3/command/reference/cpt93_cr/cpt93_cr_chapter_010.html#wp1254011620
HTH -
We are facing serious problems related to MPLS MTU. Due to fragmentation some of the applications are not working. I have enabled the mpls mtu 1508 across the path of MPLS but some of our switches do not support jumbo frames.
The strange this is that we are not only facing this issue with customer which are connected with us via Ethernet (wireless and cable) but also customers having WAN connection like ATM.Hi Ahmede...
We had a similar issue with Windows 2000/2003 platforms. In our case, it was a Microsoft bug which a patch fix it... However, we don't manage the Microsoft servers, so we decided to pursue this with a solution in the router. Fragmentation was the main cause, and fixed the problem by adding the following command to the interfaces :
ip tcp adjust-mss 1272
We are still working to identify why '1272', but if you ping from some PCs you can have a payload of up to 1400+, but from other workstations (mine is an XP) I could do only 1272. Hope this helps. -
Layer 3 Etherchannel and MPLS MTU
Greetings,
If two 7609 are connected through layer 3 giga etherchannel and 7609-1 sends a frame with 1514 bytes plus two MPLS header to 7609-2, does the command mpls mtu 1522 under the giga etherchannel interface on both routers is enough?
Or it is necessary to add the global command system jumbomtu 1522 and the interface command mtu 1522 under physical gigainterfaces participating on the channel?
Cisco docs say many platforms will accept frames higher than 1500 bytes (up to 24 bytes) to accommodate control flags; that is why I am considering just mpls mtu xxx is enough.
Also, reading Cisco doc I understood that system jumbomtu xxxx and mtu xxxx should be used together. I tested sending frames higher than 1514 bytes (without MPLS tags) and system jumbomtu xxxx alone was not enough, ping failed; it was necessary to add mtu xxxx under the interface. Do you have a different experience?
Thanks,
Alaerte Gladston Vidali
IBM Global Services - SO
Tel.55+11+2121-2879 Fax:55+11+2121-2449Hi
We had some peculiar exp with 7600 (7609/7606) boxes in which we did change the physical mtu of the interface instead of mpls mtu.
Again that did the trick for us even in 7200 where we monitored the same kinda behaviour..
regds -
MPLS MTU issue (diagram attached)
Dear Experts ,
I'm trying to run MPLS between two 7206 vxr router which is connected behind a Foundry Big Iron L3 router which is configured as a L2 device .
I put on my 7206 as
int gi0/1
ip address 172.16.14.1 255.255.255.0
mpls ip
mpls mtu 1526
But it seems that there is tag assiging ,but traffic like https didn't work after that . is there is any clue ?
Regards
HarisHi ,
There is no way to increase the MTU size on foundry . But it's giving me some error
BigIron1(config-if-e1000-1/8)#ip mtu 1526
Error - 1526 not between 576 and 1500
BigIron1(config-if-e1000-1/8)#mtu ?
Unrecognized command
How can know that whether the foundry supporting giant packets / not ? . I think it's not supporting giants , the following is the output of ping sweep from one cisco router to other one .
If it's not supporting giants what will happens to my mpls packets with size 1508 ? . Is it possible me to put the command "mpls mtu 1500" ,so that mpls mtu will limit to 1500
router1#ping
Protocol [ip]:
Target IP address: 213.12.90.1
Repeat count [5]: 1
Extended commands [n]: y
Source address or interface: 213.12.83.137
Set DF bit in IP header? [no]: y
Sweep range of sizes [n]: y
Sweep min size [36]: 1450
Sweep max size [18024]: 1550
Sweep interval [1]:
Type escape sequence to abort.
Sending 101, [1450..1550]-byte ICMP Echos to 213.12.90.1, timeout is 2 seconds:
Packet sent with a source address of 213.12.83.137
Packet sent with the DF bit set
Success rate is 45 percent (46/101), round-trip min/avg/max = 20/44/120 ms
the ping is same with and without DF bit set after enabling MPLS . But before enabling tag switching as I remember I was able to ping without DF Bit set
Regards
Haris -
I need to change the MTU on a router 7507 interface (VIP4-80 card with PA-2FE) using the "mpls mtu 1508", but it is on a production network, so I need to know:
Does this command cause the router to reset the FE ports? or the VIP card? or everything is transparent to the router?
Please let me know because I have to do it ASAP.
Regards
Alex"mpls mtu" or "tag-switching mtu" will not reset the VIP or the Interface (based on personal experience on 75xx series running 12.0 (23) Service Provider IOS) . You don't have to be concerned with resets. Obviously it has the potential to impact your MPLS traffic but increasing it can only help your cause. It certainly won't make thing worse. Good luck.
-
Hello I am facing a strange issue and would be grateful to have any advice on this please.
I have an existing setup where Site A and site B are connected within an MPLS setup:
When I ping from Site B to site A with size 1500 it works no problem
ping vrf Data1 192.168.230.2 size 1500
Type escape sequence to abort.
Sending 5, 1500-byte ICMP Echos to 192.168.230.2, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 496/496/500 ms
there is a new site C that has come up with a new link as a back up of site B but when i ping it only allows ping of 1496 and not anything more.
ping vrf Data1 192.168.230.2 size 1496
Type escape sequence to abort.
Sending 5, 1496-byte ICMP Echos to 192.168.230.2, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 500/502/504 ms
ping vrf Data1 192.168.230.2 size 1497
Type escape sequence to abort.
Sending 5, 1497-byte ICMP Echos to 192.168.230.2, timeout is 2 seconds:
Success rate is 0 percent (0/5)
I have compared the configs and they are setup with same MPLS mtu size show as follows
Site B
interface FastEthernet2/0
no ip address
duplex full
speed 100
mpls label protocol ldp
mpls ip
mpls mtu 1524
end
Site C
interface FastEthernet0/1
no ip address
ip flow ingress
load-interval 30
duplex full
speed 100
mpls label protocol ldp
mpls ip
mpls mtu 1524
end
I have asked the provider of the circuit and they say that the MTU sizes on their devices are 1530 same as the link from site B because the switches connected to both the above routers have system MTU as 1530.
I cannot find out what the issue could be ?
any help on this will be much appreciated.
many thanks in advance.Site A is 7206
Site B is 7206 and
Site C is 2811
1) Directions failing is both directions
When i debug the ip icmp echo
it comes back on Site A router as
*Oct 24 14:08:57.872 UTC: ICMP: dst (10.181.0.1) port unreachable rcv from 10.181.3.105
the utilization on Site C is as follows: could it be a reason why large sized packets are failing?
100 ** * * ** * * * * * * * * * ** *
90 ** * * ***** * * * * * *** * * * * **** *
80 #****** ** **###** ** **** ****#*** * **** ** *##** **
70 #####*** ** *######********#** * **####***#*****#** ** *###***##
60 #######********###########*#####*******###############*** ****#########
50 ##########**#####################***####################******##########
40 ########################################################################
30 ########################################################################
20 ########################################################################
10 ########################################################################
0....5....1....1....2....2....3....3....4....4....5....5....6....6....7..
0 5 0 5 0 5 0 5 0 5 0 5 0
CPU% per hour (last 72 hours)
* = maximum CPU% # = average CPU%
I have checked the configs and compared with the Site B configs and they seem to good. I have validated with someone else as well.
How do I check if there are places where more than one label is being used? -
Dealing with Fixed Length formats both at sender and receiver side
Hi all,
I have file -- File with fixed lenght formats.
Source system will generate a text file with fixed lenght and target also needs the same file with same format.
Then we have an idea to implement the interface with out IR Development .this is fine upto now.
But now the problem is we are receiving more fields from source than we require for target process. we are not using at receiver side.
So receiving system needs only few required fields from the source file.
From soucre
Ex: Source.... DocNum Invoice No Bill date Bill amount vendor code
We require at target
Ex: Target..... DocNum Bill Date Vendor code
Please suggest me
RegardsHi,
>>The source file content conversion is simple...In the target when you specify the target field names just leave out the ones you dont need...
from source we wil read all the fields, this is fine and in the target how to mention the field positions
Here all fields will come into picture, we cant mention the positions at receiver
Source side Ex: Docnum InvoiceNo Billdate Bill Amt Vendor
Fixed lenghts are 10 20 10 10 20
Target Expects Ex: Docnum BillDate Vendor
10 10 20
in receiver side if you mention fixed lenghts like 10 10 20 means it may read docnum, Invoiceno, BillDate
It wont ignore InvoiceNo field in this case
Regards -
Confused about mpls mtu command
hi,
i confuse about mpls mtu command
test platforms are 76 pfc3b,mpls,gigabit sip400 spa interface
if i didn't config mpls mtu command ,using default,ping command is successful,if more than 1496 packets, i can see fragment from show ip traffic.
if i config mpls mtu override 1504,ping command is sucessful too. there is fragment too when i use 1501 byte packet.
if i config mpls mtu override 1524 byte.
ping command failed if i use packet more than 1500, , all packet are droped,even 1501 byte.only 1500 byte packet can success.
all config above interface mtu is 1500.
this confused me.
why i use default 1500 interace mtu, mpls mtu override 1504 ,ping packet can fragment,ping success, but i use mpls mtu override 1524, i can see fragment in show ip traffic,but ping command failed. i can't see packet in destination router,how this work.
thank you!
juntopology is simple
7609-1--sip GE spa----7609-2--pos---7609-3--flexwan E1-----7604-1--ge--ce
i config mpls mtu 1524 between 7609-1 and 7609-2 . and keep interface mtu 1500 default.
ping packet from 7609-1 to 7604-1 loopback 0.
ping 1500 byte packet is ok, but ping 1501 byte packet is totally lost.then i config mtu 1524 between 7604-1 and 7609-3, it is useless,notwork, i can't see packet coming from 7609-1 on 7604-1.
but i add config mtu 1524 between 7609-1 and 7609-2. config mtu 1500 between 7604-1 and 7609-3,ping 1501 bytes from 7609-1 to 7604-1 loopback0 is ok. but i can see fragment from show ip traffic command in 7609-3.
i have a question, why we need mpls mtu command. if we don't change interface mtu,just only config mpls mtu 1524, it doesn't work, if we just change mpls mtu,how it work in the ios. if we config interface mtu 1524,interface mtu size is big enough, it seems mpls mtu command is useless, we don't need mpls mtu command, just interface mtu 1524 is ok.
why we need mpls mtu command. we just only change interface mtu is enough.
thank you!
jun -
Why we need mpls mtu command?
if interface mtu is not big enough to take mpls packet. we just increase interface mtu. why we need mpls mtu command.
if we just only increase mpls mtu.there is problem if mpls mtu biger than interface mtu. so it seem mpls mtu command is useless.
why we need mpls mtu command!
thank you!
JunHi,
i test it in netowork,like this\
topology is simple
7609-1pe--sip GE spa----7609-2p--pos---7609-3p--flexwan E1-----7604-1pe--ge--ce
i config mpls mtu 1524 between 7609-1 and 7609-2 . and keep interface mtu 1500 default.
ping packet from 7609-1 to 7604-1 loopback 0.
ping 1500 byte packet is ok, but ping 1501 byte packet is totally lost.then i config mtu 1524 between 7604-1pe and 7609-3, it is useless,not work, i can't see packet coming from 7609-1 on 7604-1.
then i add config mtu 1524 between 7609-1pe and 7609-2. config mtu 1500 between 7604-1 and 7609-3,ping 1501 bytes from 7609-1 to 7604-1 loopback0 is ok. but i can see fragment from show ip traffic command in 7609-3.
i have a question, why we need mpls mtu command. if we don't change interface mtu,just only config mpls mtu 1524, it doesn't work, if we just change mpls mtu,how it work in the ios. if we config interface mtu 1524,interface mtu size is big enough, it seems mpls mtu command is useless, we don't need mpls mtu command, just increase interface mtu 1524 is ok.
why we need mpls mtu command. we just only change interface mtu is enough.
when i config mpls mtu override 1524,this is a warning in ios:
Setting the mpls mtu to 1524 on interface serial1/0/0:0, which is higher than the interface MTU
1500. This could lead to packet forwarding problems including packet drops.
You must set the MPLS MTU values equal to or lower than the interface MTU values.
thank you!
jun -
MPLS MTU on various ethernet controllers
Is there some documentation available which router ethernet interface controller supports which maximum frame size ?
Background:
We have some intra-PoP crossover FE connections in an MPLS VPN based network. To avoid fragmentation we'd like to increase the mpls mtu to e.g. 1520bytes. I know that this isn't an issue on a PA-2FE-TX (7206-VXR), but there are also c3745 used as PE / P boxes. Does anybody know what frame sizes the onboard FEs of the 3745 and the NMs of these platforms (e.g. NM-2FE2W) can support ?
There is a document available for switches on CCO:
http://www.cisco.com/warp/public/473/148.html
Something in that style whould be great ...
thanks,
StefanAny update on this ?
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