Dear fellow ciscosians
I enabled MTU size of 9198 bytes with the system mtu 9198 command on a IOS XE 3850 Catalist Switch (WS-C3850-12X48U / iOS 03.07.04E)
But i can only send frames with size 8106 bytes from a SVI to another switch. Is there anything i've missed? The old system mtu routing command doesnt exist anymore, so i think this sould be handled by the system mtu command now.
Pinging another Switch over a tengig copper connection:
switch1#ping 172.27.5.2 size 8107 df-bit repeat 2
Type escape sequence to abort.
Sending 2, 8107-byte ICMP Echos to 172.27.5.2, timeout is 2 seconds:
Packet sent with the DF bit set
..
Success rate is 0 percent (0/2)
switch1#ping 172.27.5.2 size 8106 df-bit repeat 2
Type escape sequence to abort.
Sending 2, 8106-byte ICMP Echos to 172.27.5.2, timeout is 2 seconds:
Packet sent with the DF bit set
!!
Success rate is 100 percent (2/2), round-trip min/avg/max = 1/5/10 ms
It works if i ping myself:
switch1#ping 172.27.5.3 size 9198 df-bit repeat 2
Type escape sequence to abort.
Sending 2, 9198-byte ICMP Echos to 172.27.5.3, timeout is 2 seconds:
Packet sent with the DF bit set
!!
Success rate is 100 percent (2/2), round-trip min/avg/max = 1/1/1 ms
switch1#ping 172.27.5.3 size 9199 df-bit repeat 2
Type escape sequence to abort.
Sending 2, 9199-byte ICMP Echos to 172.27.5.3, timeout is 2 seconds:
Packet sent with the DF bit set
..
Success rate is 0 percent (0/2)
Here are some outputs of the interfaces:
switch1#show interfaces Te3/0/48
TenGigabitEthernet3/0/48 is up, line protocol is up (connected)
Hardware is Ten Gigabit Ethernet, address is 0076.86c7.6030 (bia 0076.86c7.6030)
MTU 9198 bytes, BW 10000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 10Gb/s, media type is 100/1000/2.5G/5G/10GBaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 13000 bits/sec, 23 packets/sec
5 minute output rate 4000 bits/sec, 7 packets/sec
6086128 packets input, 435168231 bytes, 0 no buffer
Received 6059779 broadcasts (6059092 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 6059092 multicast, 0 pause input
0 input packets with dribble condition detected
2068116 packets output, 146994833 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
switch2#show interfaces tenGigabitEthernet 3/0/48
TenGigabitEthernet3/0/48 is up, line protocol is up (connected)
Hardware is Ten Gigabit Ethernet, address is 0076.86b5.15b0 (bia 0076.86b5.15b0)
MTU 9198 bytes, BW 10000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 10Gb/s, media type is 100/1000/2.5G/5G/10GBaseTX
input flow-control is off, output flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:25, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 4000 bits/sec, 7 packets/sec
5 minute output rate 13000 bits/sec, 23 packets/sec
2068705 packets input, 147036703 bytes, 0 no buffer
Received 2042317 broadcasts (2041638 multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 2041638 multicast, 0 pause input
0 input packets with dribble condition detected
6087885 packets output, 435293579 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
switch1#show system mtu
Global Ethernet MTU is 9198 bytes.
switch2#show system mtu
Global Ethernet MTU is 9198 bytes.
Has this something to do with MGIG or why is this limitation. I seem to be the only one with the 8106 byte limit, because i didnt find anyone with the same problem.
Thanks for any feedback.
