Peter van Oene wrote: > > > > Nov 14 11:51:14.121 ESuT: OSPF: Rcv DBD from x.x.x.x on > Channel6/0 seq > > 0x3DCDF2DA opt 0x2 flag 0x7 len 32 mtu 0 state EXCHANGE > > Nov 14 11:51:14.121 ESuT: OSPF: Send DBD to x.x.x.x on > Channel6/0 seq > > 0x3DCDF2DA opt 0x42 flag 0x2 len 1472 > My money is on either the mtu mismatch (master seems confused > here) or > the multicast nature of dbd process cause folks to get > confused. > > Bit 2 in options is the E bit where set (0x2) means stub and > unset means > normal area.
After sending my message, I did some sniffing of books and RFCs and packets with both EtherPeek and the NAI Sniffer and discovered that the OSPF Options field has been in flux over the years. As a former programmer, I would start with Bit 0. That's the low-order bit in the 2^0 place. Doyle in Routing TCP/IP, and the NAI Sniffer, call Bit 0 the T bit. Is is supposedly used to specify whether the router supports routing based on the Type of Service bits. RFC 2328 says that bit is undefined, I was glad to see. (Routing based on the TOS bits never panned out). Bit 1, or the bit in the 2^1 place, is the E bit. Both routers in this scenario are setting it. > Both agree on the stubbiness of the area, so that > should > be fine. Bit 3 is the O bit and setting it refers to ones > capability > with opaque LSAs. Calling it Bit 3 is confusing. It's in the other nibble, for one thing. It should be called Bit 6 and it is the Opaque (O) bit, per RFC 2370, as you mentioned. The Sniffer got this right. Doyle and EtherPeek don't mention it. This won't help JMcL (sorry) but here's how the option bits are defined per RFC 2370: * | O | DC | EA | N/P | MC | E | * | E-bit This bit describes the way AS-external-LSAs are flooded. MC-bit This bit describes whether IP multicast datagrams are forwarded. N/P-bit This bit describes the handling of Type-7 LSAs. DC-bit This bit describes the router's handling of demand circuits. EA-bit This bit describes the router's willingness to receive and forward External-Attributes-LSAs. O-bit This bit describes the router's willingness to receive and forward Opaque-LSAs. Sorry if this was a BIT to bit-picky. ;-) I agree with Peter that MTU seems the suspicious issue. Of course, MTU should have different values depending on which layer you are referring to and it's hard to know what one specific configuration for a particular implementation (like on the mainframe) expects, so this could certainly be an area for concern. Let us know what you find out JMcL. Thanks. Priscilla Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=57476&t=57410 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
