Cisco – MTU Sweep

Super cool feature if you have GRE going through an Encryptor or other encryption/tunnels.

Simply type ping and press enter at your IOS prompt:

Switch#ping
Protocol [ip]:
Target IP address: 10.0.1.1
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]: y
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]: y
Sweep min size [36]: 1300
Sweep max size [18024]: 1600
Sweep interval [1]:
Type escape sequence to abort.
Sending 300, [1300..1600]-byte ICMP Echos to 10.0.1.1, timeout is 2 seconds:
Packet sent with the DF bit set
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!M.M.M.M.......
Success rate is 86 percent (93/107), round-trip min/avg/max = 57/68/72 ms

 

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