Cisco 300-410 Practice Test - Questions Answers, Page 17

Overview of the IPv6 First-Hop Security Binding Table

A database table of IPv6 neighbors connected to the device is created from information sources such as NDP snooping. This database, or binding table, is used by variousIPv6 guard features to validate the link-layer address (LLA), the IPv4 or IPv6 address, and the prefix binding of the neighbors to prevent spoofing and redirect attacks.

IPv6 First-Hop Security Binding Table Recovery MechanismThe IPv6 first-hop security binding table recovery mechanism enables the binding table to recover in the event of a device reboot.

Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_fhsec/configuration/15-s/ip6-fhs-bind-table.html

If a router is configured to get the time from a Network Time Protocol (NTP) server, the times in the router's log entries may be different from the time on the systemclock if the [localtime] option is not in the service timestamps log command. To solve this issue, add the [localtime] option to the service timestamps log command. Thetimes should now be synchronized between the system clock and the log message timestamps.

Reference: https://community.cisco.com/t5/networking-documents/router-log-timestamp-entriesare-different-from-the-system-clock/ta-p/3132258

--------------------------R1--------------------------------------------- interface Ethernet0/0 ip address 209.165.201.1 255.255.255.0 ip access-group EGRESS2 out ipv6 address 2001:DB8::1/64 end ---------------------- R2-------------------------------------------------- interface Ethernet0/0 ip address 209.165.201.25 255.255.255.0 ipv6 address 2001:DB8::2/64 ipv6 address autoconfig ipv6 nd autoconfig default-route ipv6 nd cache expire 60 ipv6 nd ra suppress ipv6 traffic-filter INGRESS in end IOU_Router2#telnet 2001:DB8::1 Trying 2001:DB8::1 ... Open IOU_Router1> ------------------------------------------------------------------------------

The set ip default next-hop command verifies the existence of the destination IP address in the routing table, andÖ+ if the destination IP address exists, the command does not policy route the packet, but forwards the packet based on the routing table.+ if the destination IP address does not exist, the command policy routes the packet by sending it to the specified next hop.

Reference: https://www.cisco.com/c/en/us/support/docs/ip/ip-routed-protocols/47121-pbr-cmdsce.html

From the output of the "show ip eigrp topology Ö" command, we notice network 192.168.13.0/24 was learned via two routes:+ From 192.168.23.3 (R3) with FD = 1075200 and AD = 281600+ From 192.168.12.1 (R1) with FD = 2611200 and AD = 281600 From the output of the "show ip route Ö" command, we learned that the best (and chosen) path is via 192.168.23.3 (R3).

To use both paths (called unequal cost load balancing) with EIGRP, the second path via R1 must satisfy the feasibility condition. The feasibility condition states that, theAdvertised Distance (AD) of a route must be lower than the feasible distance of the current successor route.

In this case, the second path satisfies the feasible condition as its AD (281600) is smaller than the FD (1075200) of the best path. Therefore we can configure loadbalancing with "variance" command.

In other words, EIGRP will install all paths with metric < variance * best_metric into the local routing table, provided that it meets the feasibility condition to preventrouting loop. Therefore we can calculate the variance > metric / best_metric = 2611200 / 1075200 =2.4.

So with a variance greater than 2 (and must be an integer), we can load balance traffic to network 192.168.13.0/24.