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

loose source record route option in ip header ,still puzzled

I was reading  rfc 791 ( internet protocol)  .  I am still puzzled about  loose source record option

I will use en example to make my point.

let say we have a network as shown below.

H1---------e0R1s0--------------------------s0R2---------H2

Where  H  denotes host and  R  denotes router.

Let say  R1 receives the packet on e0 from H1, with Loose source record option with  ip1,ip2  listed in the route field.

pointer in the option points to to ip1,  R1  replaces the  ip address in the destination ip address field with ip1, increments the pointer by 4.

Here is my confusion,  according to rfc, R1 will replace the  ip1 with recorded route address in the option data field

According to rfc,  the recorded route address is the internet module's own internet address as known  in the enviroment into which this datagram is being forwarded.

It  all seems greek to me.


How will R1 replace the ip1 ?  will it replace it with ip address of e0 or  so?

thanks a lot.

http://http://www.rfc-archive.org/getrfc.php?rfc=791

1 ACCEPTED SOLUTION

Accepted Solutions

Re: loose source record route option in ip header ,still puzzl

I was reading  rfc 791 ( internet protocol)  .  I am still puzzled about  loose source record option

I will use en example to make my point.

let say we have a network as shown below.

H1---------e0R1s0--------------------------s0R2---------H2

Where  H  denotes host and  R  denotes router.

Let say  R1 receives the packet on e0 from H1, with Loose source record option with  ip1,ip2  listed in the route field.

pointer in the option points to to ip1,  R1  replaces the  ip address in the destination ip address field with ip1, increments the pointer by 4.

Here is my confusion,  according to rfc, R1 will replace the  ip1 with recorded route address in the option data field

According to rfc,  the recorded route address is the internet module's own internet address as known  in the enviroment into which this datagram is being forwarded.

It  all seems greek to me.


How will R1 replace the ip1 ?  will it replace it with ip address of e0 or  so?

thanks a lot.

Hi,

Loose Source Routing is an IP option which can be used for address translation.Loose source routing uses a source routing option in IP to record the set of routers a packet must visit. The destination of the packet is replaced with the next router the packet must visit. By setting the forwarding agent (FA) to one of the routers that the packet must visit,

The name loose source routing comes from the fact that only part of the path is set in advance.This is in contrast with strict source routing, in which every step of the route is decided in advance when the packet is sent.

Check out the below link for example :-

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f22.shtml

Hope to Help !!

Ganesh.H

2 REPLIES

Re: loose source record route option in ip header ,still puzzl

I was reading  rfc 791 ( internet protocol)  .  I am still puzzled about  loose source record option

I will use en example to make my point.

let say we have a network as shown below.

H1---------e0R1s0--------------------------s0R2---------H2

Where  H  denotes host and  R  denotes router.

Let say  R1 receives the packet on e0 from H1, with Loose source record option with  ip1,ip2  listed in the route field.

pointer in the option points to to ip1,  R1  replaces the  ip address in the destination ip address field with ip1, increments the pointer by 4.

Here is my confusion,  according to rfc, R1 will replace the  ip1 with recorded route address in the option data field

According to rfc,  the recorded route address is the internet module's own internet address as known  in the enviroment into which this datagram is being forwarded.

It  all seems greek to me.


How will R1 replace the ip1 ?  will it replace it with ip address of e0 or  so?

thanks a lot.

Hi,

Loose Source Routing is an IP option which can be used for address translation.Loose source routing uses a source routing option in IP to record the set of routers a packet must visit. The destination of the packet is replaced with the next router the packet must visit. By setting the forwarding agent (FA) to one of the routers that the packet must visit,

The name loose source routing comes from the fact that only part of the path is set in advance.This is in contrast with strict source routing, in which every step of the route is decided in advance when the packet is sent.

Check out the below link for example :-

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f22.shtml

Hope to Help !!

Ganesh.H

New Member

Re: loose source record route option in ip header ,still puzzled

I don't think your question was answered reg. how will R1 replace the IP1. The link to PING and TRACEROUTE commands provides somewhat basic info. Not much about the topic in question(in my opinion).

 

When R1 determines that next IP in source route is s0 of R2 it sets the s0(R2) as a destination address in IP header, replaces the first address in IP options(which was originally that of R1 e0) by the IP address of the interface the datagram will be forwarded on(in this case s0 of R1) and the pointer is incremented by 4.

 

 

1640
Views
0
Helpful
2
Replies
CreatePlease login to create content