nanog mailing list archives
Re: rfc 1812 third party address on traceroute
From: William Herrin <bill () herrin us>
Date: Wed, 1 Jun 2016 17:42:02 -0400
On Wed, Jun 1, 2016 at 5:03 PM, Octavio Alvarez <octalnanog () alvarezp org> wrote:
On 05/31/2016 11:22 AM, William Herrin wrote:I'm not sure if you mean that, if sent through C it should have the source addres of A, or that it should actually be sent through A regardless of the routing table (which sounds better to me).That doesn't make sense. There may be multiple next hops out A. If the next hop in the FIB is out C, how would the router pick the next hop to send to out A?Back to the physical address that sent the TTL-offending packet.
Howdy, That would be an example of a layer violation. The only guarantee that layer 2 makes to layer 3 is that if you tell the layer 2 stack the layer 3 next hop address on that lan segment, it can figure out where to deliver your packet (via arp on ethernet, but this is not necessarily true of other layer 2s). Long story short, layer violations break things. Indeed, many of BGP's thornier problems and the mess that is mobile routing can all be traced to a single layer violation that TCP commits on IP. Regards, Bill Herrin -- William Herrin ................ herrin () dirtside com bill () herrin us Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>
Current thread:
- Re: rfc 1812 third party address on traceroute Marc Storck (Jun 01)
- Re: rfc 1812 third party address on traceroute William Herrin (Jun 01)
- Re: rfc 1812 third party address on traceroute Marc Storck (Jun 01)
- <Possible follow-ups>
- Re: rfc 1812 third party address on traceroute Octavio Alvarez (Jun 01)
- Re: rfc 1812 third party address on traceroute Hugo Slabbert (Jun 01)
- Re: rfc 1812 third party address on traceroute William Herrin (Jun 01)
- Re: rfc 1812 third party address on traceroute Octavio Alvarez (Jun 01)
- Re: rfc 1812 third party address on traceroute Randy Bush (Jun 01)
- Re: rfc 1812 third party address on traceroute Randy Bush (Jun 05)
- Re: rfc 1812 third party address on traceroute Josh Reynolds (Jun 05)
- Re: rfc 1812 third party address on traceroute Randy Bush (Jun 05)
- Re: rfc 1812 third party address on traceroute Josh Reynolds (Jun 05)
- Re: rfc 1812 third party address on traceroute William Herrin (Jun 01)