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New Member

MLPPP with Higher MTU then 1500 without Fragmentation

Dear,

I am trying to set-up an MLPPP sessie with an MTU higher than 1500 but without fragmentation. The link between PE and CPE supports MTU upto 1530

Concrete situation in testlab is as following

Cisco 7200 with NPE-400 acting as BRAS connected to an Cisco 2900 on his FastEthernet0/1

MTU size on the FastEthernet0/1 is 1530

MTU size on the Gig0/0 of the 2900 is 1530 as well

PE Config

interface FastEthernet0/1

mtu 1530

no ip address

speed auto

duplex auto

pppoe enable group radius-1

no cdp enable

end

bba-group pppoe radius-1

virtual-template 2

tag ppp-max-payload minimum 1492 maximum 1600

interface Virtual-Template2

mtu 1510

ip unnumbered FastEthernet0/0

peer default ip address pool default

keepalive 20

ppp mtu adaptive

ppp lcp echo mru verify

ppp authentication pap radius-1

ppp authorization radius-1

ppp accounting radius-1

ppp multilink

ppp multilink fragment disable

ppp multilink mrru local 1510

CPE Config

interface GigabitEthernet0/0

mtu 1530

no ip address

duplex auto

speed auto

pppoe enable

pppoe-client dial-pool-number 1

end

interface Dialer0

mtu 1510

ip address negotiated

ip virtual-reassembly

encapsulation ppp

dialer pool 1

dialer-group 1

ppp authentication pap callin

ppp pap sent-username ********* password 0 ***************

ppp multilink

ppp multilink fragment disable

ppp multilink mrru local 1510

!

The session comes online and I am seeing an MTU of 1510 on both sides (CPE and PE)

PE

Virtual-Access4 is up, line protocol is up

  Hardware is Virtual Access interface

  Interface is unnumbered. Using address of FastEthernet0/0 (188.118.4.252)

  MTU 1510 bytes, BW 200000 Kbit/sec, DLY 100000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation PPP, LCP Open, multilink Open

  Open: IPCP

  MLP Bundle vaccess, cloned from Virtual-Template2

  Vaccess status 0x44, loopback not set

  Keepalive set (20 sec)

  DTR is pulsed for 5 seconds on reset

  Last input 00:00:08, output never, output hang never

  Last clearing of "show interface" counters 00:00:45

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     15 packets input, 9568 bytes, 0 no buffer

     Received 0 broadcasts (0 IP multicasts)

     0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     15 packets output, 9982 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 unknown protocol drops

     0 output buffer failures, 0 output buffers swapped out

     0 carrier transitions

CPE

Virtual-Access4 is up, line protocol is up

  Hardware is Virtual Access interface

  MTU 1510 bytes, BW 112 Kbit/sec, DLY 20000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

  Encapsulation PPP, LCP Open, multilink Open

  Stopped: CDPCP

  Open: IPCP

  MLP Bundle vaccess, cloned from Dialer0

  Vaccess status 0x44, loopback not set

  Keepalive set (10 sec)

  DTR is pulsed for 5 seconds on reset

  Interface is bound to Di0 (Encapsulation PPP)

  Last input 00:00:14, output never, output hang never

  Last clearing of "show interface" counters 00:00:53

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

  Queueing strategy: weighted fair

  Output queue: 0/1000/64/0 (size/max total/threshold/drops)

     Conversations  0/1/16 (active/max active/max total)

     Reserved Conversations 0/0 (allocated/max allocated)

     Available Bandwidth 84 kilobits/sec

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 0 bits/sec, 0 packets/sec

     16 packets input, 9616 bytes, 0 no buffer

     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     16 packets output, 10054 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 unknown protocol drops

     0 output buffer failures, 0 output buffers swapped out

     0 carrier transitions

So far so good, however, I am not able to transport any packet bigger then 1500 with DF-Flag enabled

yourname#ping 188.118.4.252 size 1500 df-bit

Type escape sequence to abort.

Sending 5, 1500-byte ICMP Echos to 188.118.4.252, timeout is 2 seconds:

Packet sent with the DF bit set

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms

yourname#ping 188.118.4.252 size 1501 df-bit

Type escape sequence to abort.

Sending 5, 1501-byte ICMP Echos to 188.118.4.252, timeout is 2 seconds:

Packet sent with the DF bit set

.....

Success rate is 0 percent (0/5)

yourname#

Any ideas?

Everyone's tags (5)
1 REPLY
New Member

MLPPP with Higher MTU then 1500 without Fragmentation

Found an solution, however, It looks to be a bug.

When applying Cisco-avpair += lcp:interface-config#1=ip mtu 1510 trught radius on the user, I am able to ping upto 1510.

As well as I enter ip mtu 1510 under the Virtual Template after the session has been setup.

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