D-Link xStack DES-3800 Series User Manual page 138

Authentication
Hello Packet
Hello packets are OSPF packet type 1. They are sent periodically on all interfaces, including virtual
links, in order to establish and maintain neighbor relationships. In addition, Hello Packets are
multicast on those physical networks having a multicast or broadcast capability, enabling dynamic
discovery of neighboring routers.
All routers connected to a common network must agree on certain parameters such as the Network
Mask, the Hello Interval, and the Router Dead Interval. These parameters are included in the hello
packets, so that differences can inhibit the forming of neighbor relationships. A detailed explanation of
the receive process for Hello packets is necessary so that differences can inhibit the forming of
neighbor relationships.
The format of the Hello packet is shown below:
Field
Network Mask
Options
Hello Interval
Router Priority
Router Dead Interval
xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch
A 64-bit field used by the authentication scheme.
Hello Packet
Version No.
Checksum
Hello Interval
Figure 8- 17. Hello Packet
Description
The network mask associated with this interface.
The optional capabilities supported by the router.
The number of seconds between this router's Hello packets.
This router's Router Priority. The Router Priority is used in the
election of the DR and BDR. If this field is set to 0, the router is
ineligible become the DR or the BDR.
The number of seconds that must pass before declaring a
silent router as down
1
Packet Length
Router ID
Area ID
Authentication Type
Authentication
Authentication
Network Mask
Options
Router Dead Interval
Designated Router
Backup Designated Router
Neighbor
122
Router Priority