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how is tunnel checksum calculated?

johncheung
Level 1
Level 1

does anyone know how the the tunnel checksum is calculated?...it it md5?

john

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Accepted Solutions

thisisshanky
Level 11
Level 11

If you are referring to GRE, then it uses 1's complement method to calculate the checksum. Zero the checksum field, take the 1's complement sum of the payload + GRE header, then take a 16 bit 1's compliment of the previous result, to get the final checksum.

Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus

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1 Reply 1

thisisshanky
Level 11
Level 11

If you are referring to GRE, then it uses 1's complement method to calculate the checksum. Zero the checksum field, take the 1's complement sum of the payload + GRE header, then take a 16 bit 1's compliment of the previous result, to get the final checksum.

Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus
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