6 - IPv4 Routing Flashcards
What is a CSU/DSU?
Channel service unit/Data service unit
What is an SFP port?
Small Form Pluggable port. Allows you to choose a an SFP that supports the type of cabling provided by the Ethernet WAN provider opposed to the other standard RJ-45 port that supports copper cabling (implied for LAN)
What is a notable difference between Cisco Routers and Switches with regards to power?
Switches typically do not have an on/off switch
What two features are SOHO Routers likely to have that Enterprise routers typically are less likely to have?
- SOHO routers almost always use Internet and VPN technology for their WAN connections to send data back and forth to rest of the Enterprise
- SOHO routers typically use a multi-function device that does routing, LAN switching, VPN, wireless, etc
Do Cisco switches have Aux ports?
No
What is the difference in default settings for Telnet and SSH between Routers and Switches?
Routers default to disallow Telnet and SSH
Switches allow Telnet and SSH by default
What devices support the show mac address-table
command?
Switches. Routers do not.
What is the difference between show interfaces status
on a Switch and Router?
On a switch the command lists one line of output per interface. But on a Router a different command must be used (show ip interface brief)
What is the difference between the show interfaces status
command and show ip interface brief
command?
The first command is used on a Switch while the second lists similar information on routers
What does each status code mean for an interface status? e.g. up/up
Line Status/Protocol Status
- Line Status refers to whether Layer 1 is working
- Protocol Status is mainly Data Link protocol (L2)
What could it mean if the Line Status is down?
Cable issues, devices not powered on
What could it mean if the Protocol Status is down?
Mismatched data-link layer configuration e.g. PPP vs HDLC, or could be down if the Line Status is down
What does it mean if the line status is Administratively down?
The interface has a shutdown command configured on it
What kind of information does the show protocols
command show?
State of the router interfaces (Line Status/Protocol Status)
IP address and mask
What do Aux ports do?
Works like a console port. But typically connected through a cable to external analog modem, which in turn connects to a phone line
What command do you use to configure the Aux port?
line aux 0
What two things does a router consider when receiving a data link frame?
- If it has no Frame errors (FCS field)
2. Frames destination data link address is the router’s address or appropriate multicast/broadcast address
Why do routes for remote subnets typically list both an outgoing interface and next-hop router IP address?
Because routes for subnets that connect directly to the router do not need to be sent to another router so they can list only an outgoing interface
What is a connected route?
A route added because of the configuration of a the ip address
command
What is a static route?
A route added because of the use of the ip route
global command
What is a local route?
Host route - A route that defines a route for just that one IP (has /32 prefix). Used for the routers interface on that subnet.
What two facts must be true for the router to automatically add a route to its routing table for the subnet connected to each interface?
- Interface is in a working state (up/up)
2. Interface has IP address assigned through ip address
command
What is the routing protocol code for OSPF?
O
What is the Prefix another name for?
Subnet ID
What does the router use its ARP table for?
Transmitting packets to hosts connected to the same subnet as the router
What is the default timeout for an ARP entry on Cisco IOS?
240 minutes
How do you show the ARP table on a router?
show ip arp
What command is used to configure static routes?
ip route
When is a static route considered a ‘network route’?
When the destination specified defines a subnet, or entire Class A, B or C network
What is a default route?
A route that matches all destination IPs e.g. 0.0.0.0
What is a host route?
A route that matches a single IP address
How do you show only static routes from the routing table?
show ip route static