Volume 2 - Chapter 8: Applied IP ACLs Flashcards
A network engineer wants create an ACE entry to match the following:
* Permit Rule
* Traffic from 10.0.0.0 /8 subnets to any other subnet
* Permit only echo request messages
* Line 50
What would be the required command to implement this in a named extended ACL?
50 permit icmp 10.0.0.0 0.0.0.255 any echo
A network engineer wants create an ACE entry to match the following:
* Permit Rule
* Traffic from 10.0.0.0 /8 subnets to subnet 172.23.22.0 /23
* Permit both echo request and reply messages
* Line 50
What would be the required command to implement this in a named extended ACL?
50 permit icmp 10.0.0.0 0.0.0.255 172.23.22.0 0.0.1.255 echo
60 permit icmp 10.0.0.0 0.0.0.255 172.23.22.0 0.0.1.255 echo-reply
True or False:
OSPF message packets can only be filtered by inbound ACLs
True, routers do not forward OSPF packets.
A network engineer wants create an ACE entry on Router to match the following:
* Permit OSPF messages from Router 1 (172.19.2.6)
* Deny OSPF messages from all other routers
* Permit both echo request and reply messages from any other router
* Start at line 50
What would be the required command to implement this in a named extended ACL?
50 permit ospf host 172.19.2.6 any
60 deny ospf any any
70 permit icmp any any
PC1 is connected directly to Router 1 which acts as a DHCP relay server
What are the source and destination ports before and after the relay forwards the request?
PC1 will send a segment with a source port of 68 and a destination port of 67
Router 1 will receive the request and forward it to its configured DHCP server with a source and destination port of 67
PC1 is connected directly to Router 1 which acts as a DHCP relay server to Server 1
What are the source and destination IPs before and after the relay forwards the request?
PC1 will send a segment with a source IP of 0.0.0.0 and a destination IP of 255.255.255.255
Router 1 will receive the request and forward it to its configured DHCP server with the following:
* Source IP: Router 1’s outgoing interface
* Destination IP: Server 1’s IP address
True or False:
DHCP request IP being changed by a router due to a configured ip helper bypass any outgoing ACL.
True, an outgoing ACL on a router’s interface will not prevent it from forwarding a DHCP request.
Describe how ACLs function with routers that are configured as DHCP relays.
A router will process any inbound ACLs before modifying the IP source/destination information DHCP packet before forwarding it off.
A network engineer wants create an ACE entry on Router to match the following:
* Permit any source IP to ports 40 to 50
* Destination of any 192.168.x.x network
* Start at line 450
What would be the required command to implement this in a named extended ACL?
450 permit ip any 192.168.0.0. 0.0.255.255 range 40 50
What are the commands to apply an access-class to all VTY lines with the following?:
* Match inbound
* Name of access-classs is SSH-PERMIT
line vty 0 15
access-class SSH-PERMIT in
What are the commands to configure an access-class to all VTY lines with the following?:
* Match outbound
* Name of access-classs is SSH-DENY
* Deny all destination IPs
* Use line 15
ip access-list SSH-DENY
15 deny any
line vty 0 15
access-class SSH-DENY out
What are the commands to configure an access-class to all VTY lines with the following?:
* Match inbound
* Name of access-classs is SSH-PROTECT
* Permit all class A private networks
* Deny all class B private networks
* Permit all private class C networks
* Start at line 20, incrementing by 10
ip access-list SSH-PROTECT
20 permit 10.0.0.0 0.255.255.255
30 deny 172.16.0.0 0.240.255.255
40 deny 192.168.0.0 0.0.255.255
line vty 0 15
access-class SSH-PROTECT in
A network technician configures an access-list with the following commands:
ip access-list extended my-acl
permit tcp 192.168.144.128 0.0.0.240 any
deny tcp 10.0.0.0 0.255.255.255 any eq telnet
What will be the default sequence numbers assigned to each ACE entry?
“show access-list my-acl” provides the following output:
10 permit tcp 192.168.144.128 0.0.0.240
20 deny tcp 10.0.0.0 0.255.255.255 any eq telnet
Describe how ACL persistance differs between IOS and IOS-XE.
With IOS, ACEs are automatically resequenced by 10 after every reload
IOS-XE has ACL persistance on by default and needs to be disabled to allow for automatic ACE resequencing on a reload.
What is the command to disable ACL persistance on an IOS-XE router?
no ip access-list persistent