Refer to the exhibit.
The network administrator can see the DHCP discovery packet in R1, but R2 is not replying to the DHCP request. The R1 related interface is configured with the
DHCP helper address. If the PC is directly connected to the Fa0/1 interface on R2, the DHCP server assigns as IP address from the DHCP pool to the PC.
Which two commands resolve this issue? (Choose two.)
The issue described involves the DHCP relay agent on R1 and communication with the DHCP server on R2. Two commands would help resolve this issue. First, the 'service dhcp' command enables the DHCP server and relay functionality on the device, ensuring that the relay agent can forward DHCP requests properly. Second, the 'ip dhcp relay information trust-all' command on R2 allows the DHCP server to process requests with a zero giaddr field, which can occur in relayed packets. These commands together will help ensure that DHCP packets are correctly processed and an IP address can be assigned to the DHCP client through the relay agent.
Answer is D and E https://community.cisco.com/t5/switching/cisco-router-configured-as-a-dhcp-server-not-replying-to-quot/td-p/3206932 1.- The relay agent was configured by default with "no service dhcp". This caused the relayed packets to come from 0.0.0.0 rather than 10.2.1.1 2.- The DHCP server needs to be configured with "ip dhcp relay information trust-all" so it processes relayed packets with no Giaddr field
See https://community.cisco.com/t5/switching/cisco-router-configured-as-a-dhcp-server-not-replying-to-quot/td-p/3206932
D & E for sure, references: ip dhcp relay information trust-all : This command is useful if there is a switch in between the client and the relay agent that may insert option 82. Use this command to ensure that these packets do not get dropped. https://www.cisco.com/en/US/docs/ios/12_4t/ip_addr/configuration/guide/htdhcpre.html Prerequisites for Configuring the Cisco IOS DHCP Relay Agent: The Cisco IOS DHCP server and relay agent are enabled by default. You can verify whether they have been disabled by checking your configuration file. If they have been disabled, the no service dhcp command will appear in the configuration file. Use the service dhcp command to reenable the functionality if necessary. https://content.cisco.com/chapter.sjs?uri=/searchable/chapter/content/en/us/td/docs/ios-xml/ios/ipaddr_dhcp/configuration/15-sy/dhcp-15-sy-book/configuring_cisco_ios_dhcp_relay_agent.html.xml
Labbed it and none of the answers worked
I have done the same, put the configs and activate dhcp snooping only in the access switch with the uplink port in trust but nothing works, on the core switch I enabled the service dhcp and in the router with dhcp enabled I used the command ip dhcp relay information trust all
the dhcp packets are not relayed from the dhcp relay agent switch, after removing the dhcp snooping in the switch everthing is working fine (in the access switch)
ok actually I will go for D and E even if is not gonna work in the real enviroment. Actually with these commands the relay agent will see that the giaddr field is zero and is not gonna relay nothing even with the command ip dhcp relay information trust-all. What you need to do for solve this issue is just use the command "ip dhcp relay information trusted" in the vlan of the core switch. That command is gonna let the core switch accept the dhcp packet even with giaddr set to zero and is gonna put the ip address of the switch in the giaddr field.
Answer is D and E
Option correct D and E https://www.cisco.com/en/US/docs/ios/12_4t/ip_addr/configuration/guide/htdhcpre.html#wp1027171
there in no ip dhcp relay information enable command. #ip dhcp relay information trusted ?? (config-if)#ip dhcp relay information ? check-reply Validate relay information in BOOTREPLY option DHCP relay information option option-insert Insert relay information in BOOTREQUEST policy-action Define reforwarding policy trusted Received DHCP packet may contain relay info option with zero giaddr (config-if)#ip dhcp relay information trusted
Answer is D and E. B command does not exist. It is considered that snooping is set for the l2 switch, so E is required on R2.
B & E.. A - isn't a command C - isn't a real command and depends on the IOS if it supports option 82. D - is wrong, that command enables the DHCP server and its on R1 which is the relay agent. B adds the DHCP relay agent information option which is (option 82) which is additional info about the relay agent. E allows for requests to process that has a zero for the giaddress.
If the relay agent inserts option 82 but does not set the giaddr field in the DHCP packet, the DHCP server interface must be configured as a trusted interface by using the ip dhcp relay information trusted command. This configuration prevents the server from dropping the DHCP message. More info on why its B & E
I agree with DE
D and E are correct A doesn't exit B doesn't exit C doesn't exit R2(config)#service dhcp-relay ? % Unrecognized command R2(config)#service dhcp-relay R2(config)#ip dhcp option ? % Unrecognized command R2(config)#ip dhcp option R2(config)#ip dhcp relay information ? check Validate relay information in BOOTREPLY option Insert relay information in BOOTREQUEST policy Define reforwarding policy trust-all Received DHCP packets may contain relay info option with zero giaddr R2(config)#ip dhcp relay information R2(config)#service dhcp R2(config)#