Network Services Flashcards
What are the four steps in a DHCP exchange
DORA: Discover Offer Request Acknowledgement
How do you set an interface to use DHCP
ip address dhcp (activate by restarting the interface)
How do you configure a router to become a DHCP server
ip dhcp pool pc IP address / subnet mask
make sure to provide default router interface
What are a few properties of HSRP
A Cisco proprietary first hop redundancy protocol
Essentially, a host has a default gateway to get off a subnet but if the router goes down, the pc cannot connect outside of their subnet
As a result you can connect the host to many other “routers”/layer 3 switches such that if one goes down the other one can be operated: both switches in active mode have IP address and Mac address of virtual router
What if the interface of a router/layer3 switch goes down?
A feature called interface tracking can monitor an interface then dynamically change the priority of the switch
What is an active router and what is the default priority
An active router is the router with highest priority and the default priority is 100.
What if a router/layer 3 switch goes down or breaks?
The other backup router will know via hello messages not send after the hold time that the router has broken down
What does preempt do?
If a router is initially up but breaks and then goes back up, it can restore its position as the active router because it had an initially higher priority
Set up two routers with HSRP
standby (group number) ip (virtual address)
standby 10 priority (priority)
standby 10 preempt
trace route
How do you see which router is the active router within HSRP
show standby brief
What versions of HSRP support what IP
HSRP version 1 supports only IPv4 HSRP version 2 supports IPv6
What is a stratum number
The believability of a time source
What is a highly believable stratum number
1
How does stratum number change across devices
each device adds one to the stratum number from the device they learn it from
