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An extended IOS ACL must allow HTTPS from 192.0.2.10 to 198.51.100.20 but deny other traffic from 192.0.2.0/24. The first current ACE is `deny ip 192.0.2.0 0.0.0.255 any`. Which edit preserves the exception?
Cisco ACLs process ACEs in order and stop on the first matching entry. The specific permit must precede the broader matching deny so approved HTTPS traffic reaches it.
The broad deny matches the approved source first; a later permit cannot be reached for the same packet.
Logging a deny does not permit the required connection; an explicit allow ACE is still needed before the broad denial.
Implicit deny blocks unmatched traffic, including the desired HTTPS flow unless an explicit permit is placed before it.
At a research campus, the migration lead must permit only device 10.45.42.38 as a source in a standard IPv4 ACL. Which ACE uses IOS host matching correctly?
The host keyword is equivalent to wildcard 0.0.0.0 and matches only IPv4 address 10.45.42.38; this is the requested single-source permit.
This `host` selector identifies only 10.45.42.39, whereas the requirement names 10.45.42.38. One-off differences in the last octet still designate a different IPv4 source.
Wildcard 0.0.0.255 matches an entire last-octet range, not exactly 10.45.42.38. It is overly permissive.
Deny blocks the exact source host when the requirement is to allow it.
At a university, a network operations engineer is choosing placement for a standard IPv4 source ACL covering 10.65.15.0/24; only one destination segment should be restricted. Which practice is most suitable?
A standard IPv4 ACL matches only source addresses, so destination-side placement can reduce unintended blocking for 10.65.15.0/24 traffic to unrelated services. Interface context still determines the actual direction.
Repeating a broad source-only filter on upstream interfaces causes avoidable collateral outages for unrelated destinations.
This location filters the source at a broad point in its path, denying access to unrelated destinations too. A standard source-only ACL should be scoped near the intended protected destination.
A standard IPv4 ACL cannot distinguish TCP destination ports; matching a single service requires an extended ACL and appropriate placement.
An IOS standard ACL must allow source IPv4 subnet 10.177.73.0/27 and then rely on the usual implicit deny for other sources. Which ACE matches exactly the permitted subnet?
Standard ACL 20 uses the wildcard complement 0.0.0.31 for prefix 10.177.73.0/27. This source match permits exactly the IPv4 subnet range described.
Even with correct wildcard bits, deny rejects all sources in 10.177.73.0/27; the policy requests a permit.
IOS wildcard values are not dotted subnet masks; 255.255.255.224 would mean a different set of address bits may vary.
The wildcard 0.0.0.15 is a different mask from the inverse of /27 and matches a narrower range than 10.177.73.0/27.
A router allows SSH on its VTY lines, but only administrators from subnet 192.0.2.0/24 should initiate device-management sessions. An appropriate standard ACL 15 already permits that source. Which command applies it to inbound VTY access?
An IOS VTY `access-class` can restrict which source addresses may open remote terminal sessions, while SSH authentication still applies.
`ip access-group` attaches ACLs to routed interfaces and is not the VTY `access-class` mechanism.
VLAN trunk settings are Layer 2 interface controls and do not restrict inbound IP SSH sessions on VTY lines.
An OSPF network statement controls routing-protocol interface participation, not the management-login source ACL.
At a regional hospital, the infrastructure lead needs standard IPv4 ACL 15 to permit source subnet 10.98.167.0/24 before applying an implicit deny. Which ACE matches the requested source range?
The wildcard 0.0.0.255 is the bitwise inverse of subnet mask 255.255.255.0, matching all sources in 10.98.167.0/24. A standard ACL matches source IPs rather than destination TCP ports.
Even with a correctly sized source range, deny blocks the required hosts rather than permitting them.
The subnet mask 255.255.255.0 is not the wildcard; entering it in an IOS access-list match can select the opposite bits.
This wildcard 0.0.255.255 selects a different address set than 10.98.167.0/24; the zeros/ones in the wildcard control which bits must match.
At a stadium, the on-call technician must permit only TCP connections from 10.120.113.50 to service 192.168.42.19 destination port 123 using extended ACL 145. Which ACE expresses that exact flow?
This extended ACE matches source 10.120.113.50, destination 192.168.42.19, transport tcp, and destination port 123; it permits precisely the stipulated flow.
This reverses source and destination and describes the opposite direction of traffic. Extended ACL addresses are ordered source then destination.
The fields match the flow but deny is the wrong action when the requirement is to allow it.
An ip ACE is broader than the required tcp destination port 123; it would permit unrelated protocols and ports.
At a research campus, the campus network lead has extended ACL 115 that must check packets as they enter a router interface from source network 10.153.0.0/16. Which interface command applies it in the intended direction?
Applied inbound to the specified interface, ip access-group 115 in evaluates packets arriving from 10.153.0.0/16 before local forwarding.
access-class is associated with line/VTY access filtering and is not the same interface data-plane ACL attachment.
ip helper-address forwards selected UDP broadcasts to an IP server; 115 is an ACL number, not a helper IP.
Outbound placement evaluates packets leaving the interface, not those arriving from the described upstream segment.
At a nonprofit organization, the on-call technician has a broad deny for a maintenance subnet but must allow approved host 10.97.161.32. Which ACL-ordering strategy preserves the explicit exception?
IOS ACLs are processed top-down and stop on the first match. The exception for 10.97.161.32 must appear before a covering deny if it is intended to be permitted.
An existing broad deny matching 10.97.161.32 terminates ACL evaluation before the later permit; moving the permit after it cannot restore this source's access.
The `log` modifier records a deny match; it does not permit the packet or change first-match ACL processing. A permit earlier in the list is required.
A host-specific explicit deny would block the very source 10.97.161.32 that needs the exception. The approved host needs a permit before the broader subnet deny, not another earlier deny.
At a payment processor, an implementation partner must permit only device 10.130.115.108 as a source in a standard IPv4 ACL. Which ACE uses IOS host matching correctly?
The host keyword is equivalent to wildcard 0.0.0.0 and matches only IPv4 address 10.130.115.108; this is the requested single-source permit.
Wildcard 0.0.0.255 matches an entire last-octet range, not exactly 10.130.115.108. It is overly permissive.
This `host` selector identifies only 10.130.115.109, whereas the requirement names 10.130.115.108. One-off differences in the last octet still designate a different IPv4 source.
Deny blocks the exact source host when the requirement is to allow it.
At an insurance company, the campus network lead is choosing placement for a standard IPv4 source ACL covering 10.30.143.0/24; only one destination segment should be restricted. Which practice is most suitable?
A standard IPv4 ACL matches only source addresses, so destination-side placement can reduce unintended blocking for 10.30.143.0/24 traffic to unrelated services. Interface context still determines the actual direction.
An interface description is documentation, not a packet-match field; source-only standard ACL evaluation cannot distinguish separate destination IPs.
This location filters the source at a broad point in its path, denying access to unrelated destinations too. A standard source-only ACL should be scoped near the intended protected destination.
The requirement is destination-specific; a broad placement would deny permitted traffic to other segments.
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