HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 3 - IP Routing Confi - Page 67

Figure 22 Hello packet format 0 7 Version 15 1 31 Packet length Router ID Area ID Checksum AuType Authentication Authentication Network mask HelloInterval Options Rtr Pri RouterDeadInterval Designated router Backup designated router Neighbor ... Neighbor Major fields of the hello packet are as follows: • Network mask-Network mask associated with the router's sending interface. If two routers have different network masks, they cannot become neighbors. • HelloInterval-Interval for sending hello packets. If two routers have different intervals, they cannot become neighbors. • Rtr Pri-Router priority. A value of 0 means the router cannot become the DR or BDR. • RouterDeadInterval-Time before declaring a silent router down. If two routers have different dead intervals, they cannot become neighbors. • Designated router-IP address of the DR. • Backup designated router-IP address of the BDR. • Neighbor-Router ID of the neighbor router. DD packet Two routers exchange database description (DD) packets, describing their LSDBs for database synchronization. A DD packet contains only the headers of LSAs to reduce traffic. 57