Here are some packet overhead numbers for a few popular protocols to help with doing bandwidth requirement calculations.  This may be another add-as-we-go post, so please comment with additions or corrections.

Ethernet : 20 bytes
Frame Relay : 4 - 6 bytes
PPP : 6 bytes
MLPPP: 10 bytes
MPLS : 4 bytes

IP : 20 bytes

TCP : 20+ bytes
UDP : 8 bytes
GRE:  4 - 20+ bytes

Feel free to correct.

Study Questions

• What’s the most primitive way to get traffic destined to a single host to use a different path than your dynamic IGP dictates?

Use a static route.

• What’s the most primitive way to get traffic sourced from a single host to use a different path than your dynamic IGP dictates?

Use policy-based routing (PBR).

• What’s the most primitive way to get traffic sourced from a single host and destined for another host to use a different path than your dynamic IGP dictates?

Use PBR.

I’ve seen and used the command before, but I’ve never really seen any use of the show ip protocols command until tonight while reading up for my ROUTE test.  There’s a lot of good information in the output, and, from the way the book is reading, this is a great candidate for use in a lab question.

To check it out a bit, I set up a small network with four routers connected only to a single Ethernet segment.  I set up one router to run EIGRP, OSPF, and BGP to each one of the other routers just so I could see the output for the different routing protocols.  Here’s what puked out after struggling with GNS for a few minutes.