** Interface with default MTU on WS-X6148A-GE-45AF **
WS-X6148A-GE-45AF
WS-X6748-GE-TX
HO-SW6506#sh int gi2/17 | in MTU
MTU 1500 bytes, BW 1000000 Kbit, DLY 10
usec,
HO-SW6506#sh int gi 1/17 | in MTU
MTU 1500 bytes, BW 1000000 Kbit, DLY 10
usec,
** Ping test from the 3945 to a prefix learned via OSPF/ MPLS link **
HO-RTR-3945#sh mpls forwarding-table 2.8.0.4
Local Outgoing Prefix
Bytes Label Outgoing Next Hop
Label Label or Tunnel Id Switched interface
27
explicit-n 2.8.0.4/32
0
Gi0/1.1803 10.255.250.188
** Without DF bit set **
WS-X6148A-GE-45AF
WS-X6748-GE-TX
HO-RTR-3945#ping ip
Target IP address: 2.8.0.4
Repeat count [5]: 1
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]:
Set DF bit in IP header? [no]: no
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp,
Verbose[none]: v
Loose, Strict, Record, Timestamp, Verbose[V]:
Sweep range of sizes [n]: y
Sweep min size [36]: 1480
Sweep max size [18024]: 1600
Sweep interval [1]:
Type escape sequence to abort.
Sending 121, [1480..1600]-byte ICMP Echos to
2.8.0.4, timeout is 2 seconds:
HO-RTR-3945#ping ip
Target IP address: 2.8.0.4
Repeat count [5]: 1
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]:
Set DF bit in IP header? [no]: no
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp,
Verbose[none]: v
Loose, Strict, Record, Timestamp, Verbose[V]:
Sweep range of sizes [n]: y
Sweep min size [36]: 1480
Sweep max size [18024]: 1600
Sweep interval [1]:
Type escape sequence to abort.
Sending 121, [1480..1600]-byte ICMP Echos to
2.8.0.4, timeout is 2 seconds:
Reply to request 120 (1 ms) (size 1600)
Success rate is 100 percent (121/121), roundtrip min/avg/max = 1/1/4 ms
Reply to request 15 (1 ms) (size 1495)
Reply to request 16 (1 ms) (size 1496)
Request 17 timed out (size 1497)
Request 18 timed out (size 1498)
-
Ping test is successful, the WS-X6148AGE-45AF card is able to fragment all the
packets
-
Ping test breaks at 1496 as it is not able
to fragment by default and is missing 4
bytes that are being used on the MPLS
label
** With DF bit set **
WS-X6148A-GE-45AF
WS-X6748-GE-TX
HO-RTR-3945#ping ip
Target IP address: 2.8.0.4
Repeat count [5]: 1
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]:
Set DF bit in IP header? [no]: yes
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp,
Verbose[none]: v
Loose, Strict, Record, Timestamp, Verbose[V]:
Sweep range of sizes [n]: y
Sweep min size [36]: 1480
Sweep max size [18024]: 1600
Sweep interval [1]:
Type escape sequence to abort.
Sending 121, [1480..1600]-byte ICMP Echos to
2.8.0.4, timeout is 2 seconds:
Packet sent with the DF bit set
HO-RTR-3945#ping ip
Target IP address: 2.8.0.4
Repeat count [5]: 1
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]:
Set DF bit in IP header? [no]: yes
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp,
Verbose[none]: v
Loose, Strict, Record, Timestamp, Verbose[V]:
Sweep range of sizes [n]: y
Sweep min size [36]: 1480
Sweep max size [18024]: 1600
Sweep interval [1]:
Type escape sequence to abort.
Sending 121, [1480..1600]-byte ICMP Echos to
2.8.0.4, timeout is 2 seconds:
Packet sent with the DF bit set
Reply to request 26 (4 ms) (size 1506)
Reply to request 27 (1 ms) (size 1507)
Reply to request 28 (1 ms) (size 1508)
Request 29 timed out (size 1509)
Request 30 timed out (size 1510)
Reply to request 15 (1 ms) (size 1495)
Reply to request 16 (1 ms) (size 1496)
Request 17 timed out (size 1497)
Request 18 timed out (size 1498)
Ping test breaks at 1508, even though MTU is
configured to be 1500
Ping test breaks at 1496 which is expected as no
fragmentation is taking place. Result confirms
first test
** MTU Increased **
WS-X6148A-GE-45AF
WS-X6748-GE-TX
HO-SW6506#sh int gi 2/17 | in MTU
MTU 9216 bytes, BW 1000000 Kbit, DLY 10
usec,
HO-SW6506#sh int gi 1/17 | in MTU
MTU 9216 bytes, BW 1000000 Kbit, DLY 10
usec,
** With DF bit set **
WS-X6148A-GE-45AF
WS-X6748-GE-TX
HO-RTR-3945#ping ip
Target IP address: 2.8.0.4
Repeat count [5]: 1
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]:
Set DF bit in IP header? [no]: yes
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp,
Verbose[none]: v
Loose, Strict, Record, Timestamp, Verbose[V]:
Sweep range of sizes [n]: y
Sweep min size [36]: 1480
Sweep max size [18024]: 1600
Sweep interval [1]:
Type escape sequence to abort.
Sending 121, [1480..1600]-byte ICMP Echos to
2.8.0.4, timeout is 2 seconds:
Packet sent with the DF bit set
HO-RTR-3945#ping ip
Target IP address: 2.8.0.4
Repeat count [5]: 1
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]:
Set DF bit in IP header? [no]: yes
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp,
Verbose[none]: v
Loose, Strict, Record, Timestamp, Verbose[V]:
Sweep range of sizes [n]: y
Sweep min size [36]: 1480
Sweep max size [18024]: 1600
Sweep interval [1]:
Type escape sequence to abort.
Sending 121, [1480..1600]-byte ICMP Echos to
2.8.0.4, timeout is 2 seconds:
Packet sent with the DF bit set
Reply to request 27 (1 ms) (size 1507)
Reply to request 28 (1 ms) (size 1508)
Request 29 timed out (size 1509)
Request 30 timed out (size 1510)
Reply to request 27 (4 ms) (size 1507)
Reply to request 28 (1 ms) (size 1508)
Request 29 timed out (size 1509)
Request 30 timed out (size 1510)
Ping test breaks at 1508, when the MTU is configured to be jumbo at this point the WS-X6748-GE-TX
matches the default behaviour of the WS-X6148A-GE-45AF