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

SNMP notifications can be sent as traps or inform requests. Traps are unreliable because the receiver does not send acknowledgments when this device receives traps.”Send reliable and encrypted notifications for any events” so it is SNMP notifications. For encryption we need to configure “priv”.

1. R1 received DHCP packet and its interface was configured with the DHCP helper address. But we are not sure if R1 forward DHCP packet to R2 or not. 2. If we connect PC directly to R2 then this problem will not appear -> DHCP Server function was configured on R2.

From these facts, the most likely problem is related to Option 82. Maybe R2 ignored DHCP request packets because it was receiving these packets with the giant field set to 0.0.0.0.

By default Cisco IOS devices reject packets with zero “giaddr” and by default Cisco Catalyst switches use “giaddr” of zero when configured for DHCP snooping! Reference: https://blog.ine.com/2009/07/22/understanding-dhcp-option-82

If we can run the “debug ip dhcp server packet” on R2, we may see these messages:

*Feb 22 23:54:57.759: IP: s=0.0.0.0 (FastEthernet0/1), d=255.255.255.255, len 34 4, input feature, MCI Check(64), rtype 0, forus FALSE, sendself FALSE, mtu 0, fw dchk FALSE *Feb 22 23:54:57.759: IP: s=0.0.0.0 (FastEthernet0/1), d=255.255.255.255, len 34 4, rcvd 2 *Feb 22 23:54:57.759: IP: s=0.0.0.0 (FastEthernet0/1), d=255.255.255.255, len 34 4, stop process pak for forus packet

*Feb 22 23:54:57.759: DHCPD: inconsistent relay information. *Feb 22 23:54:57.759: DHCPD: relay information option exists, but giaddr is zero

We are receiving the DHCP packet from R1, source 0.0.0.0, and destination 255.255.255.255 broadcast, but if you notice from the debug output, R2, our DHCP Server, is complaining that the relay information is inconsistent. Option 82, Information Option, is contained in the packet but the GIADDR is zero. The GIADDR stands for Gateway IP Address, which is the IP Address of the relaying agent. The Option 82, Information Option, would then contain the receiving port and hostname of the Relaying Agent by default.

R2 sees the Option 82 information, signalling that the DHCP packet might have been relayed, BUT there is no relaying IP Address. This is the behavior of DHCP Snooping when enabling it on a switch, and since the switchport does not contain an IP Address, since it’s Layer 2, no GIADDR will be added.

Instead, just the Option 82 Information is added and this is the problem we have, but there are options:

1. You could trust all on R2 the DHCP Server, which will cause the server to not be so suspicious: – ip dhcp relay information trust-all – ip dhcp relay information trusted 2. Disable theaddition of Option 82 information on SW: – no ip dhcp snooping information option 3. Trust the port that is receiving the DHCP Discover: – ip dhcp snooping trust

Any of these options will fix our predicament.

https://community.cisco.com/t5/networking-documents/how-to-configure-pbr/ta-p/3122774

Follow these guidelines when configuring the switch as an SSH server or SSH client:

+ An RSA key pair generated by a SSHv1 server can be used by an SSHv2 server, and the reverse.+ If the SSH server is running on a stack master and the stack master fails, the new stack master uses the RSA key pair generated by the previous stack master

+ If you get CLI error messages after entering the crypto key generate rsa global configuration command, an RSA key pair has not been generated. Reconfigure thehostname and domain, and then enter the crypto key generate rsa command.+ When generating the RSA key pair, the message No host name specified might appear. If it does, you must configure a hostname by using the hostname globalconfiguration command.+ When generating the RSA key pair, the message No domain specified might appear. If it does, you must configure an IP domain name by using the ip domain-nameglobal configuration command.+ When configuring the local authentication and authorization authentication method, make sure that AAA is disabled on the console.

+ allows an LSR to remove the label before forwarding the packet: penultimate hop popping

+ accepts unlabeled packets and imposes labels: label edge router

+ group of packets that are forwarded in the same manner: forwarding equivalence class

+ receives labeled packets and swaps labels: label switch router

Explanation

A label edge router (LER, also known as edge LSR) is a router that operates at the edge of an MPLS network and acts as the entry and exit points for the network. LERspush an MPLS label onto an incoming packet and pop it off an outgoing packet.

A forwarding equivalence class (FEC) is a term

Diagram Description automatically generated

The MPLS LDP Inbound Label Binding Filtering feature can be used to control the amount of

memory used to store Label Distribution Protocol (LDP) label bindings advertised by other

devices. For example, in a simple Multiprotocol Label Switching (MPLS) Virtual Private Network

(VPN) environment, the VPN provider edge (PE) devices might require label switched paths

(LSPs) only to their peer PE devices (that is, they do not need LSPs to core devices). Inbound

label binding filtering enables a PE device to accept labels only from other PE devices.

https://www.cisco.com/en/US/technologies/tk583/tk372/technologies_white_paper0900aecd802b8f3c.html

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.