High Availability Flashcards
Graceful restart works by informing OSPF neighbors that it is going to restart. The router that is going to restart is called the _________________
restarting router
(OSPF) the restarting process is called the _____________
graceful restart mode
Graceful restart initiates by sending a link-local type _ LSA called the grace LSA with a specified time called the ________
9, grace period
Two adjacent routers enter helper mode and are called the __________
helper neighbors
OSPF graceful restart is covered in RFC 3623. Before the RFC, Cisco already implemented its own version of graceful restart called ___________. Cisco IOS supports both NSF and the RFC version of graceful restart.
NSF (Non-Stop Forwarding)
Graceful shutdown - It is possible to shut down the OSPF process using ________ command and at interface level you may use _______ command
Shutdown, ip ospf shutdown
MPLS LDP GR functions strictly in ______ ____, which means it can only help other routers that are enabled with MPLS SSO/NSF and GR to recover. If the router with LDP GR fails, its peer routers cannot help it recover.
helper mode
The basic operation of LDP GR /NSF is the same as other protocols. Routers continue forwarding packets even after the LDP adjacency fails.
True
An adjacency between router LDP GR > LDP SSO/NSF > LDP GR is invalid
False, it is true
When a failure occurs and LDP GR/NSF is enabled, the entries in the LFIB are marked as stale, after the LDP session recovers the flag is removed
True
The Router announces the GR capable via Fault Tolerant flag during the session establishment
Partially false, the announcement is via TLV FT and not flag
MPLS LDP GR is supported in _________. ________________ sessions are not supported. Only LDP sessions are supported. MPLS LDP GR cannot be configured on label-controlled ___ (LC-___) interfaces.
strict helper mode, Tag Distribution Protocol (TDP), ATM
MPLS LDP GR configuration: SUMMARY STEPS 1. enable configure terminal ip cef [distributed] __________________
mpls ldp graceful-restart
Control plane could stop functioning altogether and because the forwarding plane is a separate entity with its own processors it can continue forwarding packets based on its copy of the FIB. This is ________ ______ ______ (_ _ _): The ability of the forwarding plane to continue running “headless” if the control plane stops.
Non-Stop Forwarding (NSF)
_ _ _ allows you to switch from a primary to a backup control plane without disrupting forwarding. The FIB could still become invalid during the period between when the primary control plane goes down and the backup control plane takes over, but the risk in this period is usually an acceptable compromise
NSF
The backup control plane maintains a copy of the active configuration and current state on system components such as interfaces, it can become active much faster than if it had to learn all this information first. That, then, is the second ring of our acronym circus: Cisco calls this ____ ____ ____ (_ _ _)
Stateful Switchover (SSO)
Briefly describe the function of Non Stop Routing and graceful restart
Both aim to prevent routing protocol reconvergence. They keep routing going during an RP switchover
s
For which protocols is graceful restart available?
OSPF, BGP, ISIS, LDP
Consider a BGP PE NSR Capable x CE NSR non capable Session, in case of switchover between PE RPs will the BGP session drop?
No, NSR transfers operation to another RP
To run BGP NSR the L3VPN must be configured
True
How should bfd for ospf be configured at the interface level
ip ospf bfd (only active) bfd interval 50 min_rx 50 multiplier 3
How should bfd for isis be configured at the interface level
isis bfd (only active) bfd interval 50 min_rx 50 multiplier 3
How should a bundle be configured in static mode
channel-group 12 mode on
What is the result of the configurations below: channel-group 12 mode auto channel-group 12 mode auto
No channel
What is the result of the configurations below: channel-group 12 mode desirable channel-group 12 mode auto
Channel OK PAGP
What is the result of the configurations below: channel-group 12 mode active channel-group 12 mode auto
No channel
What is the result of the configurations below: channel-group 12 mode active channel-group 12 mode passive
Channel OK LACP
Graceful restart must be enabled on both peers for NSF to operate
True. In the case of NSR, it supports one of the endpoints if the CE in an L3 VPN environment does not support NSR
In which BGP message will the NSF / graceful restart capability be announced
open
Before enabling NSF, SSO must be enabled
True
NSF is supported for both IPv4 and IPv6
False, only IPv4
NFS does not support multicast routing
True, Multicast is not SSO aware
HSRP is supported along with NSF
False
SSO can operate using RPs with different IOS versions
False, the versions must be the same
How to enable NSF in bgp?
router bgp 100 bgp graceful-restart
Default restart graceful-restart timer
120 secs
How to enable NSF in eigrp? How to enable NSF in ospf? How to enable NSF in isis?
router eigrp 100 nsf router ospf 100 nsf In isis it is necessary to inform which standard R2(config-router)#nsf? cisco Checkpoint method ietf IETF method R2(config-router)#nsf
