300-410 Exam Dumps - Cisco CCNP Enterprise Questions and Answers

A router discards BGP network prefixes if it sees its ASN in AS-Path as a loop prevention mechanism. The “allowas-in” feature allows routes to be received and processed even if router detects its own ASN in AS-Path.

After two OSPF neighboring routers establish bi-directional communication and complete DR/BDR

election (on multi-access networks), the routers transition to the exstart state. In this state, the

neighboring routers establish a master/slave relationship and determine the initial database descriptor

(DBD) sequence number to use while exchanging DBD packets.

Neighbors Stuck in Exstart/Exchange State

The problem occurs most frequently when attempting to run OSPF between a Cisco router and another

vendor’s router. The problem occurs when the maximum transmission unit (MTU) settings for

neighboring router interfaces don’t match. If the router with the higher MTU sends a packet larger that

the MTU set on the neighboring router, the neighboring router ignores the packet.

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.

After redistribution, R3 learns about network 10.1.1.0/24 via two paths:

+ Internal BGP (IBGP): advertised from R4 with AD of 200 (and metric of 0)

+ OSPF: advertised from R1 with AD of 110 (O E2) (and metric of 20)

Therefore R3 will choose the path with the lower AD via OSPF

But this is a looped path which is received from R3 -> R2 -> R1 -> R3. So when the advertised route

from R4 is expired, the looped path is also expired soon and R3 will reinstall the main path from R4.

This is the cause of intermittent connectivity.

We can solve this problem by denying the 10.1.1.0/24 prefix from being redistributed into OSPF on

R1. So R3 will not learn this prefix from R1.

Or another solution is to place an OSPF distribute-list inbound on R3 to block the 10.1.1.0/24 prefix

from being advertised back to R3.

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.

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_conn_dmvpn/configuration/15-mt/sec-conn-dmvpn-15-mt-book/sec-conn-dmvpn-dmvpn.html

By default, the maximum severity sent as a syslog trap is warning. That is why you see syslog traps for login failures. Since a login success is severity 5 (notifications), those syslog messages will not be converted to traps. To fix this, configure:

Note:

The syntax of login block is:

login block-for seconds attempts tries within seconds

Desired Min TX Interval: This is the minimum interval, in microseconds, that the local system would like to use when transmitting BFD Control packets, less any jitterapplied. The value zero is reserved.

Required Min Echo RX Interval: This is the minimum interval, in microseconds, between received BFD Echo packets that this system is capable of supporting, less anyjitter applied by the sender. If this value is zero, the transmitting system does not support the receipt of BFD Echo packets.

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15-0_2_EX/security/configuration_guide/b_sec_152ex_2960-x_cg/b_sec_152ex_2960-x_cg_chapter_01001.html

https://www.cisco.com/c/en/us/td/docs/cloud-systems-management/network-automation-and management/dnacenter/tech_notes/b_dnac_sda_lan_automation_deployment.html

https://community.cisco.com/t5/networking-documents/stateful-dhcpv6-relay-configuration-example/ta-p/3149338

In the debug output, we see that the Authorization (not Authentication) failed so we need to

correct the authorization. In order to enable authorization, we must use the global command

“aaa authorization console” first.