Cisco 300-410 - Implementing Cisco Enterprise Advanced Routing and Services (300-410 ENARSI)

--------------------------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>

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From the exhibit we see there are two flow monitors: the first one “FLOW-MONITOR-1” has been configured correctly but the second one “v4_r1” was left empty andinterface E0/0.1 is using it. So the remote server does not receive any NetFlow data.

When the aggregate-address command is used within BGP routing, the aggregated address is advertised, along with the more specific routes. The exception to this

rule is through the use of the summary-only command. The “summary-only” keyword suppresses the more specific routes and announces only the summarized

route.

DHCP options 3, 66, and 150 are used to configure Cisco IP Phones. Cisco IP Phones download their configuration from a TFTP server. When a Cisco IP Phone starts, ifit does not have both the IP address and TFTP server IP address preconfigured, it sends a request with option 150 or 66 to the DHCP server to obtain this information.+ DHCP option 150 provides the IP addresses of a list of TFTP servers.+ DHCP option 66 gives the IP address or the hostname of a single TFTP server.

From the output of the “show ip eigrp topology …” 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 …” 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.

If you configure the redistribution of OSPF into BGP without keywords, only OSPF intra-area

and inter-area routes are redistributed into BGP, by default. You can use the internal keyword

along with the redistribute command under router bgp to redistribute OSPF intra- and inter-area

routes.

Use the external keyword along with the redistribute command under router bgp to redistribute

OSPF external routes into BGP.

-> In order to redistribute all OSPF routes into BGP, we must use both internal and external

keywords. The full command would be (suppose we are using OSPF 1):

redistribute ospf 1 match internal external

Note: The configuration shows match internal external 1 external 2. This is normal because

OSPF automatically appends “external 1 external 2” in the configuration. In other words,

keyword external = external 1 external 2. External 1 = O E1 and External 2 = O E2.

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.

From the output, we learned that R1 was trying to establish BGP neighbor relationship with R3 but failed. Both of them were using physical interface to establish neighbor relationship so wedon’t need the “… ebgp-multihop” command here. The only reasonable answer is R3 has not been configured to activate BGP neighbor relationship with R1.