Thanks for the hello decode. When I have some spare time next week after my BSCI exam, I will send errors to Cisco Press as well.
Eric ----- Original Message ----- From: "Priscilla Oppenheimer" To: Sent: Wednesday, January 22, 2003 11:15 PM Subject: RE: OSPF hello implementation [7:61618] > ericbrouwers wrote: > > > > For those reading Cisco Press' CCNP Routing Exam Certification > > Guide: Sorry to > > bother you again. > > > > Chapter 4, page 178, suggests the use of TCP to exchange OSPF > > hello packets: > > > > "... To understand this complexity, it is useful to identify > > the main > > characteristics of OSPF. These key attributes of OSPF include > > the following: > > - Maintaining a connection-oriented relationship with other > > routers on the > > same physical segment. These are known as adjacent neighbors. > > This is a TCP > > connection maintained by keepalives ...." > > Oh, that's bad. > > > > > > > I haven't checked the OSPF RFC yet, but I don't believe that > > the hello > > protocol uses a TCP connection. Hello packets are implemented > > by OSPF packet > > type 1 and use IP protocol type 89 that is exclusively defined > > for OSPF > > traffic. > > You are right, indeed. Here's a printout of a Hello: > > Ethernet Header > Destination: 01:00:5E:00:00:05 > Source: 00:00:0C:05:3E:80 > Protocol Type:0x0800 IP > IP Header - Internet Protocol Datagram > Version: 4 > Header Length: 5 (20 bytes) > Type of Service: %11000000 > Precedence: Internet Cont, Normal Delay, Throughput, Reliability > Total Length: 64 > Identifier: 0 > Fragmentation Flags: %000 May Fragment Last Fragment > Fragment Offset: 0 (0 bytes) > Time To Live: 1 > Protocol: 89 OSPFIGP > Header Checksum: 0xCE95 > Source IP Address: 10.10.0.1 > Dest. IP Address: 224.0.0.5 > No IP Options > OSPF - Open Shortest Path First Routing Protocol > Version: 2 > Type: 1 Hello > Packet Length: 44 > Router IP Address: 172.16.50.1 > Area ID: 0.0.0.0 > Checksum: 0x1E8D > Authentication Type: 0 No Authentication > Authentication Data: > ........ 00 00 00 00 00 00 00 00 > Network Mask: 0xFFFFFF00 > Hello Interval: 10 seconds > Options: %00000010 > AS External Link State Advertisements > Router Priority: 1 > Dead Interval: 40 seconds > Designated Router: 0.0.0.0 No Desgntd Rtr > Backup Designated Router: 0.0.0.0 No Backup Desgntd Rtr > > > Probably authors mixed it up with BGP? > > Maybe or the other possibility is that in the author's mind > connection-oriented means TCP? > > > > > Does anyone have an errata for this cert. guide? I can't find > > it on Cisco > > Press web site. > > No. I've sent in quite a few errors on this book. I don't know why there's > no errata. > > _______________________________ > > Priscilla Oppenheimer > www.troubleshootingnetworks.com > www.priscilla.com > > > > > Thanks, > > > > Eric Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=61711&t=61618 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
