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=61620&t=61618
--------------------------------------------------
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
