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190 Cards in this Set

  • Front
  • Back
What command lists the working interfaces on which EIGRP is enabled, omitting passive interfaces?
show ip eigrp interfaces
What command lists the contest of the network configuration commands for each routing process, and a list of neighbor IP addresses?
show ip protocols
What command lists known EIGRP neighbors, omitting those with mismatched paramaters?
show ip eigrp neighbors
What command lists all successor and feasible successor routes known to the router?
show ip eigrp topology
What is the code for EIGRP learned routes in the routing table?
To what address are multicast EIGRP updates sent?
What transport protocol is used for EIGRP updates?
RTP (reliable transport protocol)
Explain the interaction between Hello interval and hold timer in EIGRP
The EIGRP hold timer is a countdown timer that is reset each time a hello message is received (one timer for each neighbor, defined by the neighbor's hello messages). When the hold timer reaches 0, the neighbor is assumed to be down.
What command shows the current values of the EIGRP hold timers?
show ip eigrp neighbors
1. What are two methods of including a connected interfaces in EIGRP without allowing neighbor relationships to form on that interface?

2. Which method is preferred, and why?
1. "passive-interface" router sub-command (preferred)
2. "redistribute connected" router sub-command

The passive-interface method is preferred because if you use the redistribute connected command, the connected networks are advertised as external routes (AD of 170).
1. What command makes all interfaces passive by default in EIGRP?

2. How do you exclude interfaces from this default?
1. passive-interface default
2. no passive-interface [interface]
What command can be used to display EIGRP passive interfaces?
show ip protocols
What do routers do with EIGRP hello messages with invalid or mismatched authentication?
Silently discard them.
What command lists the key chain configuration?
show key chain
What command can be used to determine why neighbors are failing the EIGRP authentication process?
debug eigrp packet
What command can be used to find out if an EIGRP neighbor is static?
show ip eigrp neighbors detail
What is the major side effect of configuring a static EIGRP neighbor on an interface?
The interface no longer processes EIGRP multicast packets, preventing dynamic neighborships on this interface.
Could two routers running EIGRP with different hello intervals and hold timers become neighbors?
Could mismatched IP MTU values prevent an EIGRP neighbor relationship?
Does EIGRP require exact matching subnet masks for neighborships to form?
No, but the routers must think they are on the same subnet ( and, for example, would not prevent a neighborship from forming).
What command can be used to determine EIGRP k-value weights?
show ip protocols
Can mismatched k-values prevent EIGRP neighborships?
How is the EIGRP and OSPF router-id determined?
1. Using the "eigrp router-id a.b.c.d" EIGRP subcommand
2. Using the highest IPv4 address on an up/up loopback interface
3. Using the highest IPv4 address on an up/up non-loopback interface
In what special case do EIGRP router-ids need to be unique?
When two or more routers are injecting external routes, their router-ids must not match.
List the 3 sources from which a router's EIGRP process adds prefixes to its local topology table before learning topology from a neighbor.
1. Connected subnets for interfaces on which EIGRP has been enabled.

2. Connected subnets referenced in an EIGRP neighbor command

3. Subnets learned by the redistribution of routes into EIGRP from other sources.
What are the 5 basic EIGRP protocol messages?
What information does the EIGRP update message contain?
Prefix length
Metric components (bandwidth, delay, reliability, load)
Nonmetric items (MTU, hop count)
What is the IOS default bandwidth for serial interfaces and subinterfaces?
What command protects a multiaccess frame-relay interface from being overrun with too much EIGRP message traffic?
ip bandwidth-percent eigrp
What command is used to change EIGRP metric weights?
"metric weights 0" in EIGRP configuration mode
Which EIGRP k-values are turned on by default?
K1 and K3
How do you list all possible EIGRP routes (not just successor and feasible successor)?
show ip eigrp topology all-links
What are the "eigrp stub" command options, and which are used by default?
- Connected (default)
- Summary (default)
- Static
- Redistributed
- Receive-only
What does the command "eigrp stub" do?
Prevents the router from forwarding traffic between two remote EIGRP-learned subnets.
What effect does the "eigrp stub" command have on a network with routers going active on a route?
The eigrp stub router will not respond to query messages, reducing the query scope.
Describe how the "variance" value is used in EIGRP.
Variance is multiplied by the successor's feasible distance, and any feasible successors with a metric less than the result is added to the routing table.

Routes that are not feasible successors are NOT considered, regardless of variance.
In what configuration mode is the distribute-list command issued?
router configuration mode
What command is used with EIGRP to configure route filtering?
What does the command "ip prefix-list fred permit ge 20 le 29" match?
Any routes that begin with the prefix 172.16 and have a prefix length of 20-29.
What is the prefix-length command parameter that matches all routes? le 32
What are the three methods of filtering EIGRP routes?
prefix lists
route maps
What should an EIGRP summary route metric be set to?
The lowest metric route upon which the summary route is based.
List the four benefits of EIGRP summarization
- Smaller routing tables
- Reduces EIGRP Query scope
- Can summarize at any location in the network
- The summary metric uses the best metric of all summarized routes.
List two possible problems with route summarization
- Summarization can cause suboptimal routing.
- Packets destined for inaccessible destinations may flow to the summarizing router before being discarded.
What is the command used for EIGRP route summarization, and in what configuration mode is it used?
"ip summary-address eigrp", in interface configuration mode
What happens immediately after an EIGRP summary route is configured on an interface?
The router resets its relationship with all EIGRP neighbors reachable on that interface, in order to change their topology.
What is the default AD of an EIGRP summary route?
What is the EIGRP auto-summary logic?
When a router has working interfaces in different classful networks, the router advertises a summary route for each classful network out any interfaces attached to a different classful network.
What does the EIGRP router subcommand "network" do?
Injects the default route into the EIGRP topology, ONLY if the default route is an interface (not IP address).
In what order are the OSPF "network X.X.X.X" commands processed, when determining what area an interface is in?
From most specific to least specific.
What two commands can be combined to display passive and non-passive OSPF interfaces?
show ip ospf interface brief
show ip protocols
What two multicast IPs does OSPF use, and for what purposes?
- (All SPF routers)
- (All DRs)
What are the two methods of enabling OSPF on an interface?
- "network" router subcommands.
- "ip ospf area" interface subcommands.
What are the 7 neighbor requirements for OSPF?
- Same subnet
- Same area
- Identical hello and dead intervals
- Unique router IDs
- Identical IP MTUs
- Must pass authentication (if configured)
What are the default values for the OSPF Hello interval and Dead timer on broadcast networks?
Hello: 10s
Dead: 40s
List the 6 OSPF network types.
- Broadcast
- Nonbroadcast (NBMA)
- Loopback
- Point-to-point
- Point-to-multipoint
- Point-to-multipoint nonbroadcast
List and name all of the OSPF LSA types used by Cisco routers
1 = Router
2 = Network
3 = Net Summary
4 = ASBR Summary
5 = AS External
7 = NSSA External
What is contained in a Type 1 LSA?
- The RID of the router
- A list of stub networks (networks for which no DR has been elected)
- A list of transit networks, with the IP address of the DR for each network
- The RID of any neighbors on stub networks (networks with no DR).
What is used as the LSID for a Type 1 LSA?
The advertising router's RID
What is the definition of an OSPF stub network?
A network with no DR
What is the OSPF LSID of a Type 2 LSA?
The IP of the DR's interface in that subnet.
What is the OSPF LSID of a Type 3 LSA?
The subnet number being advertised.
What command is used to limit the number of LSAs that can be learned from other routers?
What routers generate OSPF Type 2 LSAs?
The DR
What routers generate OSPF Type 1 LSAs?
Every router running OSPF
What routers generate OSPF Type 3 LSAs?
ABRs (Area Border Routers)
Explain how OSPF LSA reflooding works
If there are no changes to an LSA for 30 minutes, the LSA's owner increases the sequence number by one and refloods the LSA.
How do routers flush bad LSAs?
By setting the LSA's age to the MaxAge setting (3600) and reflooding the LSA
What are the three basic steps OSPF uses to choose the best route for a given subnet?
1. Analyze the LSDB and find all possible routes to the subnet.
2. For each possible route, add the OSPF interface costs for all outgoing interfaces in the path.
3. Pick the route with the lowest total cost.
What is the default "maximum-paths" setting for OSPF?
How do you change the reference bandwidth for OSPF?
"auto-cost reference-bandwidth" router subcommand.
In the command "area 0 filter-list XYZ in", what does "in" mean?
Filter Type 3 LSA's going IN to area 0.
What are the two types of route filtering available in OSPF?
- Type 3 LSA filtering
- distribute-list filtering
Explain OSPF distribute-list filtering.
Routes are filtered after running the SPF algorithm but before being added to the route table.
What command is used for OSPF route summarization on ABRs?
area range
What happens if you configure the OSPF "area range" command on an ABR, but no subordinate subnets exist in the area?
The ABR does not advertise the summary.
What does the "summary-address" OSPF subcommand do?
Creates a Type 5 LSA (external route) summary.
What are the two commands used to summarize OSPF routes, and when are they used?
"summary-address" is used on ASBR routers to summarize external routes.

"area range" is used on ABR routers to summarize interarea routes.
What is the most commonly used command for injecting a default route into OSPF?
default-information originate
List the four types of stubby areas in OSPF
- stub
- totally stubby
- not-so-stubby
- totally not-so-stubby
Which LSAs are filtered in which OSPF stubby areas?
Stub: Type 5
Totally Stubby: Type 5 + 3
Not-So-Stubby: Type 5
Totally Not-So-Stubby: Type 5 + 3
What OSPF command is used to set a router as Stubby
"area stub"
What OSPF command is used to set a router as Totally Stubby?
"area stub no-summary"
What OSPF command is used to set a router as Not-So-Stubby?
"area nssa"
What is the difference between a Stub area and an NSSA?
NSSAs can have external routes being redistributed inside of them
When using an OSPF virtual link, what paramaters that are normally configured on the interface can now only be configured by the "area virtual-link" command?
- authentication
- hello interval
- dead timer
What is the format of the OSPF virtual link command? Describe each of the parameters.
area <area #> virtual-link <remote-RID>

area # is the transit area (over which the virtual link will travel)

remote-RID is the other router's RID
What show commands can be used to verify OSPF virtual links?
show ip ospf virtual-links
show ip ospf neighbor [detail]
Re-read OSPF frame-relay operations section of the book.
Confusing stuff.
How does the OSPF priority work, and what command configures it?
The router with the highest priority value in the subnet automatically becomes DR, regardless of RID. Priority value 0 prevents a router from becoming DR or BDR.

"ip ospf priority" interface subcommand, range 0-255
When configuring OSPF on a single subnet with partial mesh, what special actions need to be taken to ensure that the learned routes will actually work?
All WAN routers must have frame-relay map entries for each next hop value in the routing table, or the routes will not be usable.
When using the router "redistribute" command, what sources are examined and used to find routes to redistribute?
- routing table
- connected interfaces running the redistributed protocol
What type of LSA is generated when redistributing external routes into OSPF using the router "redistribute" command?
Type 5 LSA, unless in a NSSA, where a Type 7 LSA would be generated.
What are the three options for setting metrics for route redistribution?
- "default-metric" router subcommand
- "metric" component in redistribute command
- route-map
What is the default external metric type when redistributing routes into OSPF?
How does an OSPF router choose the best route to an E2 destination with multiple paths?
It will choose the best route based on the lowest cost to reach any ASBRs that advertised the lowest E2 metric.
Read page 311-312 of ROUTE pdf
Information on OSPF E2 redistribution and metrics.
What are the default metric values for routes redistributed into OSPF?
From BGP: 1
From OSPF: source route's cost
From Other: 20
What is special about OSPF E2 routes?
No intraarea OSPF costs are added to the route.
What is the purpose of a Type 4 LSA, and what information does it contain?
To provide interarea E2 cost calculations.

It is an LSA advertised by an ABR, containing the cost to reach an ASBR in an adjacent area.
What command displays OSPF ABRs and ASBRs?
show ip ospf border-routers
For a given prefix and length, does OSPF prefer to choose an E1 route or an E2 route?
What is the difference between E1 routes and E2 routes in OSPF?
E1 routes include internal OSPF metrics, whereas E2 routes have static metrics, based on the redistribute command.
Compare the uses of E1 and E2 OSPF routes.
E1 routes can be used for load balancing based on which ASBR is closest, whereas E2 routes are best used to always direct traffic over one router (failover).
In what situation are OSPF Type 7 LSAs used?
Injecting external routes into a NSSA.
What happens to a Type 7 LSA when it leaves an NSSA?
It is converted into a Type 5 LSA
When can you use the "match" component of the router redistribute command?
When redistributing from OSPF
Use the distribute-list command to filter routes matched by ACL 100. The routes are coming from OSPF 2 and going to EIGRP 25
distribute-list 100 out ospf 2
What is the default AD for EIGRP external routes?
What is the default AD for eBGP?
What is the default AD for iBGP?
What is the default AD for an EIGRP summary route?
What does the "distance" command do?
Configure routing protocol ADs
What does the address in the "distance 171" command match when used by OSPF?
The RID of the originating router (the router that created the LSA)
What does the address in the "distance 171" command match when used by EIGRP?
The interface IP of the neighboring router that advertised the route.
When a route-map clause has no match command, what happens?
All routes are matched
Re-read IP Service Level Agreement sections!!
And add some flash cards.
List all the reserved values in the IPv4 address range.
- - self identification on a local subnet.
- - loopback testing.
- - "link local" block for default IPv4 addressing without DHCP.
- - Documentation and example code.
- - 6to4 relay.
- - benchmark testing for internet devices.
Over what port do BGP neighbors communicate?
TCP 179
What PA does BGP use by default, to choose the best route?
How does a BGP border router change the AS_PATH PA when forwarding it to a neighboring ASN?
The router adds its own ASN to the AS_PATH PA.
Describe the BGP loop prevention mechanism that uses the AS_PATH PA.
If an ASN receives a route with its own ASN listed in the AS_PATH PA, the route is ignored.
What ASN range is assignable by IANA for public use?
1 - 64,495
What ASN range is reserved for use in documentation?
64,496 - 65,511
What ASN range is for private use only?
64,512 - 65,534
What are the three different options as to what BGP routes an ISP advertises to an enterprise, and what does each consist of?
- Default routes only: Only a default BGP route.

- Full updates: The entire BGP table.

- Partial updates: Only routes for prefixes that might be better reached through that ISP, plus a default route.
What can cause a BGP neighborship to fail (or not form)?
- Incorrect neighbor statements (wrong IP or ASN)
- Duplicate BGP router IDs
- Mismatched authentication
- No TCP connection between neighbors
What is the best practice configuration when redundant links exist between BGP two neighbors?
Use loopback addresses as source and neighbor addresses.
List the BGP neighbor states and what they indicate.
1. Idle - BGP is administratively down or waiting for the next retry.

2. Connect - Attempting a TCP connection w/ neighbor

3. Active - TCP connection completed, but no BGP messages have been sent or received

4. Opensent - TCP connection is active and a BGP Open message has been sent, but one has not been received from the other router.

5. Openconfirm - Open message has been sent to and received from the other router. The next step is to receive a BGP keepalive message, confirming that all neighbor related parameters matched.

6. Established - The neighbor relationship works and the peers can exchange update messages.
List the BGP message types and what they are used for.
Open: Used to establish a neighbor relationship and exchange basic parameters.

Keepalive: Sent on a periodic basis to maintain the neighbor relationship.

Update: Used to exchange PAs and the associated prefix/length (NLRI) that use those attributes.

Notification: Used to signal BGP errors; typically resets neighbor relationship.
What command will display possible default BGP routes?
show ip bgp
What command will list possible BGP routes for a given prefix?
show ip bgp <prefix> <subnet mask>
What command will list BGP routes learned by a specific neighbor, before any inbound filtering is applied?
show ip bgp neighbors <ip-address> received-routes
What command will list BGP routes learned by a specific neighbor, after applying inbound filters?
show ip bgp neighbors <ip-address> routes
What command will list BGP routes advertised to a neighbor after applying outbound filtering?
show ip bgp neighbors <ip-address> advertised-routes
What command will list the number of BGP prefixes learned per neighbor?
show ip bgp summary
What is the BGP "network" command used for?
Injecting routes into BGP
What are the two options for advertising your public IP range into BGP when the range is split into multiple contiguous subnets (multiple routes)?
- Create a static route for the range to null0, allowing the BGP "network" command to function.

- Use the summarization featuers of your IGP to create a summary route.
What are the two options in BGP for advertising your network's public IP range?
- The BGP "network" command
- Redistribution from an IGP
What command can be used to advertise a BGP summary?
The router "aggregate-address" command.
What is the default value of iBGP next-hop addresses?
The next eBGP hop
What are two options to overcome the next-hop problem when using iBGP?
- Ensure routes exist to the next-hop address

- Use the "neighbor next-hop-self" command
What iBGP rule requires a full mesh when running BGP on more than 2 routers in the same AS?
When a router learns routes via iBGP, that router does not advertise the same routes to another iBGP peer.
After creating and applying BGP route filtering (inbound or outbound), what must happen before the filters take affect?
The BGP neighborships affected by the filtering must be reset, or "cleared".
List all commands used for clearing BGP, and explain what they do.
- "clear ip bgp *" hard clears all neighbors.
- "clear ip bgp <neighbor-id>" hard clears a specific neighbor.
- "clear ip bgp <neighbor-id> out" soft clears a neighbor in the outbound direction.
- "clear ip bgp <neighbor-id> in" soft clears a neighbor in the inbound direction, only if the router supports inbound route refresh.
- "clear ip bgp <neighbor-id> soft in" soft clears a neighbor in the inbound direction, only if "soft-reconfiguration inbound" is configured for that neighbor.
- "clear ip bgp * soft" soft clears all neighbors in both directions.
- "clear ip bgp <neighbor-id> soft" soft clears a neighbor in both directions.
What must be configured in order to use the "show ip bgp neighbor received-routes" command?
The "neighbor soft-reconfiguration inbound" BGP subcommand.
List and describe the 5 BGP PAs that affect the BGP Best Path Algorithm.
NEXT_HOP: Lists the next-hop IP address used to reach a prefix.

Weight: Not a true PA; A numeric value set by a router when receiving updates, influencing that router's route for a prefix. Not advertised.

LOCAL_PREF: A numeric value, 0 - 2^32-1, used within an AS to influence the choice of a best route for all routers in the AS.

AS_PATH: A list of all the ASNs in the path. The length (number of ASNs) is used.

ORIGIN: Value implying how the route was injected into BGP. Values = i (IGP), e (EGP), or ? (incomplete info)

MED: Multi Exit Discriminator; Set and advertised by routers in one AS, impacting decisions of routers in another AS. Smaller is better.
Under which header in the "show ip bgp" command will you find the MED value for a route?
List all the steps of the BGP best path decision process, and which values are better than others for each step, including the tiebreakers.
0. Next hop: Reachable is better (duh)
1. Weight: Bigger is better.
2. LOCAL_PREF: Bigger is better.
3. Locally injected? Locally injected is better than iBGP/eBGP learned.
4. AS_PATH length: Smaller is better.
5. ORIGIN: Prefer i is better than e, which is better than ?. i > e > ?
6. MED: Smaller is better.
7. Neighbor Type: eBGP is better than iBGP
8. IGP metric to Next_Hop: Smaller is better.
9. (tiebreaker): Oldest eBGP route wins.
10. (tiebreaker): Lowest neighbor BGP RID wins.
11. (tiebreaker): Lowest neighbor IP address wins.
Which BGP best path decision processes can be manipulated, and what routing direction do they manipulate?
Weight - outbound routes.

LOCAL_PREF - outbound routes.

AS_Path - outbound routes

MED - inbound routes (what you're advertising to your neighbors).
Describe how the BGP Weight PA can be used to influence route decisions.
Weight can be used on a single router to influence that one router's choice of outbound routes. The route with the largest Weight is chosen.
What is the range of the BGP Weight PA?
0 - 65,535 (2^16-1)
What is the default BGP Weight value?
0 for learned routes

32,768 for locally injected routes
What router sub-commands can be used for configuring the BGP Weight attribute?
"neighbor route-map" (per prefix)

"neighbor weight" (all routes learned from this neighbor)
Describe how the BGP LOCAL_PREF PA can be used to influence route decisions.
LOACL_PREF can be used to influence the best exit point from an AS for a prefix, for all routers inside the AS.
What is the range of values for the BGP LOCAL_PREF PA, and which values are better?
0 - 2^32-1

Higher values are better
What is the default value for the BGP LOCAL_PREF PA, and how do you change the default value?
Default value: 100

To change:
"bgp default local-preference"
What router subcommand is used to configure the BGP LOCAL_PREF PA?
"neighbor route-map" (the "in" option is required for updates from an eBGP peer)
How does the RTM (routing table manager) on a Cisco router choose the best route to a prefix among competing sources, and what command can be used to show BGP routes that are dropped by this process?
AD (Administrative Distance) is the discriminator.

"show ip bgp rib-failures"
Describe how the BGP AS_PATH PA can be used to influence route decisions.
It is possible to prepend values to t he AS_PATH PA using a route map, increasing the AS_PATH length.
Describe how the BGP MED PA can be used to influence route decisions.
MED allows an AS to tell a neighboring AS the best way to forward packets into the first AS. Best used on a dual-homed network.
What is the BGP MED PA value range, and default value?
Value range: 0 - 2^32-1
Default value: 0
What router subcommand, and what route-map set command is used to set the BGP MED value?
router: "neighbor route-map out"
route-map: "set metric"
What is the IPv6 global unicast range?
What is the IPv6 prefix assigned to a single company called?
global routing prefix


site prefix
What is the IPv6 multicast range?
What is the IPv6 address used by hosts to send packets to an unknown DHCP server?
List the steps of IPv6 stateless autoconfiguration.
1. Use IPv6 NDP's router solicitation and router advertisement messages to learn the prefix, prefix length, and default router.

2. Determine the interface ID portion of the IP address using the EUI-64 format.

3. Use stateless DHCP to learn DNS IPv6 addresses.
What are the RS (router solicitation) and RA (router advertisement) destination IPv6 addresses?
RS: FF02::2 (all IPv6 routers on this link)
RA: FF02::1 (all IPv6 nodes on this link)
Convert 00-1A-A0-A8-19-F2 into an EUI-64 interface ID.
Convert 0025.648D.AC79 into an EUI-64 interface ID.
What two options exist for IPv6 static IP configuration?
- Configuring the entire 128 bit address.

- Configuring the 64-bit prefix and tell the device to use an EUI-64 derived interface ID.
What are the three types of IPv6 unicast addresses, and what are their purposes and ranges?
Link Local:
- Used for sending and receiving IPv6 packets on a single subnet, such as RS and RA messages and next-hop IPs.
- Addresses are in the FE80::/10 range.

Unique Local:
- Same function as IPv4 RFC 1918 addresses (private addresses within a single organization).
- Addresses are in the FD00::/8 range.

Global Unicast:
- Identifies a single node, globally.
- Addresses in the range of 2000::/3
What are the IPv6 unspecified and loopback addresses?
Unspecified is ::/128
Loopback is ::1/128
What are the IPv6 addresses used by OSPFv3?
What are the IPv6 addresses used by RIPng?
What are the IPv6 addresses used by EIGRP?
Describe the range and format of the IPv6 solicited node multicast address.
Solicited node multicast addresses are in the range of FF02::1:FF:0/104.

The last 24 bits (6 hex digits) are taken from the last 24 bits of the IPv6 address to which the message is directed.
Describe the general process used with IPv6 to map IP addresses to MAC addresses.
IPv6 nodes use the Neighbor Discovery Protocol's multicast NS (Neighbor Solicitation) and unicast NA (Neighbor Advertisement) ICMP messages to map IPs to MACs.
How does an IPv6 interface perform Duplicate Address Detection?
The interface sends a NS message to its own solicited node multicast address. If a host replies with an identical unicast IPv6 address, there is a duplicate.
How does an IPv6 interface perform inverse neighbor discovery (determine IP from MAC)?
The sender transmits an INS message to all IPv6 hosts (FF02::1) describing the link layer address, and the specified node responds with its unicast address in an INA message.
What value is used when IOS needs a MAC address for an IPv6 enabled interface and that interface does not have a built-in MAC address?
IOS uses the MAC address of the lowest-number LAN interface on the device (eg: Fa0/0).
What issue related to the RID can cause EIGRPv6 to not run?
If there are no IPv4 addresses defined on the router, no RID is chosen, and one must be set manually before the process will run.
List the IPv6 tunneling options covered in the CCNP ROUTE material.
- Manual
- 6to4
What solution allows IPv6-only hosts to communicate with IPv4-only hosts?
NAT-PT (Network Address Translation - Protocol Translation)
When IPv4 redundancy exists on two IPv6 tunnel endpoints, from which source and destination interfaces should IPv4 addresses be borrowed, and why?
Loopback interfaces, so that when a physical interface goes down, the tunnel stays up.
What are the 5 steps for configuring a manual IPv6 tunnel?
1. Plan the IP addresses (create loopback interface if needed)

2. Create the tunnel interface ("interface tunnel <number>").

3. Define the source IPv4 address of the tunnel using the "tunnel source" interface subcommand.

4. Define the destination IPv4 address of the tunnel using the "tunnel destination" interface subcommand.

5. Define the tunnel as manually configured (not GRE) using the "tunnel mode ipv6ip" interface subcommand.
What command makes a tunnel GRE?
"tunnel mode GRE ip"


no command at all; tunnels default to GRE
How is the link local IPv6 address calculated for Manual and GRE tunnels?
Manual: FE80::/96 plus 32 bits from the tunnel source IP.

GRE: EUI-64, using the lowest numbered interface's MAC address.
What configuration differences exist when creating an automatic 6to4 tunnel, vs a manual tunnel?
- You do not define a destination IPv4 address.
- "tunnel mode ipv6ip 6to4"
- Create a static route for 2002::/16 out the tunnel interface and enable IPv6 routing.