Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

Bronze

DF bit in ip header

HI every body!

I just want to ask one question. " don't fragment " bit is set or not set by default in ip header?

thanks a lot and have a nice weekend!

5 ACCEPTED SOLUTIONS

Accepted Solutions
Silver

Re: DF bit in ip header

Usually its not set. However, some applications would default to setting it.

Thanks.

Blue

Re: DF bit in ip header

Sarah:

RFC 791 makes no mention of the default setting for the DF bit in the flags field of the IP header.

It depends on the application.

New Member

Re: DF bit in ip header

Here is what I saw

IP header from the host had DF set

IP header in a RIP response from the router

not set.

Thanks

Mat

Hall of Fame Super Silver

Re: DF bit in ip header

In my experience there is not a generic default for the TTL. It is application or vendor dependent. I have seen a lot of implementations that start at 255, and quite a few that start at 64, and some start at 128.

HTH

Rick

Blue

Re: DF bit in ip header

The TTL is set to a value by the source that represents the maximum number of hops it wants for the datagram. Each router decrements the value; if it ever reaches zero the datagram is said to have expired and is discarded.

No default. The TTL is set by the application.

8 REPLIES
Silver

Re: DF bit in ip header

Usually its not set. However, some applications would default to setting it.

Thanks.

Blue

Re: DF bit in ip header

Sarah:

RFC 791 makes no mention of the default setting for the DF bit in the flags field of the IP header.

It depends on the application.

New Member

Re: DF bit in ip header

Here is what I saw

IP header from the host had DF set

IP header in a RIP response from the router

not set.

Thanks

Mat

Blue

Re: DF bit in ip header

Matt;

Im sure you're trying to convey a message with that post. What that message is, however, I have no idea! :-)

New Member

Re: DF bit in ip header

I was hoping the experts would explain the why and why not.

Apologize for the confusion.

Bronze

Re: DF bit in ip header

Thanks all of you!

if you guys don't mind, i have a more question.

what is default value for ttl in ip header?

Thanks a lot and have a great weekend!

Hall of Fame Super Silver

Re: DF bit in ip header

In my experience there is not a generic default for the TTL. It is application or vendor dependent. I have seen a lot of implementations that start at 255, and quite a few that start at 64, and some start at 128.

HTH

Rick

Blue

Re: DF bit in ip header

The TTL is set to a value by the source that represents the maximum number of hops it wants for the datagram. Each router decrements the value; if it ever reaches zero the datagram is said to have expired and is discarded.

No default. The TTL is set by the application.

2403
Views
0
Helpful
8
Replies
CreatePlease to create content